Resident Evil: The Mercenaries 3D

Gameplay wise The Mercenaries plays much like Mercenary Mode from Re4 and Re5 with streamlined controls however unlike Mercenary Mode on the console games the characters have stats attached to them and eventually you can unlock the weapon set from other characters for use on any character.

Characters
Using Chris as the standard since he is the only character that takes 100% damage from enemies the character in order of how good they are (Comparing the percent of healing change they get to the change in damage they receive, i.e. if somebody takes 50% damage to be equal to Chris on they would need to heal 150 which is 50% of the amount Chris heals per herb to be equal to Chris) All characters have 1000 health.
Format is
Percent change compared to Chris
Character - Percent Damage Taken from enemies - Amount Healed

+50%
Rebecca Chambers (Nurse) - 150% - 600

+20%
Chris Redfield (Pilot) - 90% - 330
Rebecca Chambers - 130% - 450

+10%
Claire Redfield - 110% - 360
Jill Valentine (Casual) - 120% - 390

0
Barry Burton (Patriotic) - 130% - 390
Chris Redfield - 100% - 300
Claire Redfield (Suit) - 80% - 240
Jill Valentine - 110% - 330

-10%
HUNK (Reaper) - 70% - 180
Jack Krauser - 80% - 210
Jack Krauser (Exo-skeleton) - 60% - 150
Albert Wesker - 110% - 300

-20%
Albert Wesker (Uroboros) - 50% - 90
HUNK - 90% - 270

-30%
Barry Burton - 90% - 180

Skills
Medic
50% more vitality recovery
Level 3
Recover Vitality on Critical Hit
*Best used on characters with a high recovery rate such as Rebecca otherwise Toughness is generally going to be a better option. The threshold where Toughness becomes a better option is 250, the alternative effect for toughness tends to be better in terms of getting a score and as an added bonus Toughness means less wasted healing when using herbs defensively so I'd recommend have at least 360 healing to consider using Medic. Uroboros Wesker can make effective use of the Vitality on Critical Hit  since he has such large damage reduction and so little healing via herbs, but in that case it's usually wiser to use Friendship (if it's a map that you won't lose points by staying fairly close)

Toughness
25% Damage Reduction
Level 3
Combo Timer extension on kill
*The combo timer extension should be roughly 2 extra seconds which can be quite useful, if you're having trouble staying alive Toughness is a good option that will not only keep you alive, but still offer a small benefit to your score potential.

Luck
60% resistance to insta-kill
Level 3
All 3 skills equipped extend to your partner
*Luck is a great skill for co-op passing your other 2 skills can effectively mean you each get 5 skills instead of 3 though Luck is generally lack-luster itself it can help for those having trouble with Super Salvadors or Executioners. The main reason to use it is for team synergy, but if your partner isn't using a like skill then you could be hurting yourself the exception for this is if you partner is a much better player then letting them use 5 good skills + your Luck effect can really impact your score more for the better compared to taking 3 good skills yourself. In either case make sure you coordinate with your teammate as like named skills do not stack.

Handgun Technique
Handgun Handling improved
Level 3
+30% Critical Rate
*Actively harmful at level 3, criticals are generally poor as they cost you the opportunity to melee kill to gain more time, in terms of killing however a high critical rate is quite lethal if you are accurate. It can be used in a pinch to keep the combo going in a panic, but it's still luck-based in those high pressure scenarios. Handling is generally not very important, reduced recoil is pretty useless on a handgun, but being able to bring the gun to your eye faster helps when coming out of a melee to keep strings going without getting hit.

Handgun Custom
+30% Firerate and +50% Capacity for handguns
Level 3
+8% Weapon Damage
*Useful if not taking a skill that lets you skip reload animation, but in general a strong skill for keeping the combo going letting you fire faster when the combo is dying and for longer periods of time. Adding the Weapon Damage is icing on a lot of kits, adding damage to high powered weapons can really help it's not really useful for Machine Guns or Handguns however so some kits don't get benefit from it such as HUNK's

Shotgun Technique
Shotgun Handling Improved
Level 3
10% Damage Reduction
*One of the most useful Handling Skills bringing the shotgun to your eye faster can really help you from taking damage in a pinch and 10% Damage Reduction is useful for those who are struggling, it's a pretty good skill for beginning players.

Shotgun Custom
+30% Weapon Damage and +50% Capacity for Shotguns
Level 3
15% more vitality recovery
*Not an extremely useful skill it does turn shotguns into more or less one shot for weak mobs which is really a negative, vs bosses shotguns are actually a poor weapon since you seldom are able to get close enough to get all the pellets to hit them to do maximum damage. 15% more recovery rounds out the skill as a good beginner skill, but your score will suffer without melee attacks.

Machine Gun Technique
Machine Gun Handling Improved
Level 3
+15% Melee Damage
*Melee Damage is one of the most important aspects of the game so adding Melee Damage is huge the 'main' effect is just icing really. Handling on Machine Guns is the most important as it helps keep them on their mark which helps when walking and you can't manually adjust your reticle without stopping.

Machine Gun Custom
+30% Weapon Damage and +50% Capacity for Machine Guns
Level 3
Increase Explosive Blast Radius
*Basically custom tailored for Rebecca Chambers, the improved Damage and Capacity help her kill since she doesn't have insta-kill melee attacks and the Blast Radius improves her Grenade Launcher which helps you keep the combo going while fighting a boss, it can be a negative causing you to flinch and/or deal damage to yourself and/or your co-op partner so make sure you can handle the grenade launcher before equipping or you won't be helping anybody.

Rifle Technique
Rifle Handling Improved
Level 3
+15% Melee Damage
*Bringing the rifle to your eye faster and reducing your shaking is nice, but not needed, it's your power weapon and shouldn't be used very often. Machine Gun Technique has the same alternative effect and helps a weapon that is more practical.

Magnum Technique
Magnum Handling Improved
Level 3
30% Resistance to insta-kill
*Handling can help, but the Magnums should only be used on bosses which are all fairly large targets and it's side-effect is fairly lack luster, it's really a wasted skill.

Bomber
+30% Explosion Damage
Level 3
10% Damage Resistance
*Good skill for Rebecca, the Grenade Launcher is one of the best boss killers in the game and on top of improving it, it makes Grenades more reliable emergency kill weapons. Everybody can get advantages from this skill, but unless you're Rebecca there are better more reliable skills out there such as Giant Killer since Grenades are primarily used to stun bosses.

Combat
+40% Melee Damage
Level 3
+10% Reload Speed for all Weapons
*Hands down one of the best skills in the game, improving Melee Damage helps all characters to a degree, obviously it's more important for those without an insta-kill Melee as they need their Melee Damage to kick in to get those extra seconds, but Melees can add a lot of damage to boss enemies and there are going to be scenarios where it is easier to hit a weak spot that doesn't lead to your insta-kill for the characters who have access to them.

Smart Reload
+20% Reload Speed for all Weapons
Level 3
Reload in various situations
*The Reload Speed is pretty moot since the real benefit comes from being able to instantly reload during any animation which is representative of how in the past you could combine ammo into the gun to circumvent reload animations which was fairly 'cheap' in the previous games and mimicing that is just as 'cheap' in this one except to use it you absolutely have to be in an animation, but you don't have to have good timing just the standard reload buttons will instantly reload your gun this time around so those who couldn't reload by combining on the console can still use it in this one to have one of the most broken skills. Other skills have the same side effect and they have a different main effect that can give a bonus rather than sitting stagnant most of the time even if there is the rare occasion you might need to manually reload still it's pretty useless with the Level 3 effect.

Technician
Handling for all weapons improved
Level 3
+15% vitality recovery
*Better Recovery isn't too bad and handling for all weapon types can be nice, but in general you don't need handling, the weapon that benefits most Machine Guns has a better Level 3 effect on it's specific skill already.

Full Burst
+15% Weapon Damage for all Weapons
Level 3
Partner receives same effect
*Unlike Luck the Partner only gets the +15% Weapon Damage, it's a good effect all around and passing it to your partner isn't a bad thing, but there are better skills out there if you feel like being selfish though certain weapons are hard to get a bonus such as the Electric Grenade Launcher so Claire's Set can take good advantage of it as can Rebecca who can appreciate the added Damage for her Grenade Launcher as well as for her weak machine gun.

Weapon Master
Double Skill Effect for Weapons, but recovery is halved
Level 3
+30% Insta-kill Resistance
*Useful if you're stacking weapon skills and don't get hit a lot, but since it comes with a negative I'd say there are ways to get more benefits than using this skill plus the Level 3 benefit lowers the efficiency of using it stacked with other weapons skills a bit. If you need to heal a lot this skill will basically make you fail time after time after time, but Uroboros Wesker heals so little as is he can pull it off and with his version of the Samurai Edge pretty much every headshot can kill in a single shot.

Reversal
Access to Finisher Melee when in red HP
Level 3
+20% Ammo Capacity
*Depending on your character it can be useful, those with high Damage Resistance can afford to stay in the red longer, but it also depends on your characters Finisher Melee, but I'd highly recommend not using it on any character that takes higher than 100% damage since being in red is an invitation to going into dying status on the next attack.

Revenge
+90% Critical Hit Rate when in red HP
Level 3
Reload in various situations
*A complicated skill good on Uroboros Wesker who can stay in red and has a naturally high Crit Rate on his Pistol, but Crits tend to be harmful, one of the best side-effects for Level 3. Having a way to quickly kill in trouble isn't the worst thing ever though so it tends to not be actually be harmful if you make it a point to get out of red life, pairs well with Medic.

Giant Killing
+50% Damage vs Boss enemies
Level 3
+10% Reload Speed for all Weapons
*A great skill, Bosses can really screw up combos if you can't deal with them quickly and they tend to be the only really dangerous enemies.

Adrenaline
+2 Seconds for Combo Timer when taking damage
Level 3
+60% Damage Boost after Taunt for 6 seconds
*A solid skill if you can manage your taunts, some taunts are much shorter than others and are easier to gain the benefits, the benefits are really only useful for killing bosses which generally requires distance between you and them before taunting. Extending the Combo Timer when taking damage can really keep it from losing the combo if you get hurt while in the panic to get a kill to keep it going.

Lucky 7
+3 Seconds on a kill when a 7 is displayed on the timer (Doesn't work if the time remaining is 7 minutes)
Level 3
+10% Firerate for all Weapons
*Hands down the best skill for increasing score potential. If you can't manage your combo string then you may want to use something else, but if you can adding +3 seconds is up to 3000 points per kill or if it can be the difference between killing all enemies and missing a few either way it adds points, adding to your fire rate also gives a benefit for combo particularly shooting enemies from a distance to keep the timer going.

Close Range
+3 seconds to Combo Timer when an enemy is defeated at close range
Level 3
+60% Damage after taunt for 6 Seconds
*Like Lucky 7 if you want to Maximize your score Close Range is a must have, you should be using Melee attacks to kill enemies which does trigger Close Range giving you more time to get your next skill, the increased Damage after taunt can be useful for killing bosses if you can manage using your taunt, keep in mind the average taunt is about 2 seconds or so abusing taunts can drain your time.

Old School
Temporary Invincibility when picking up an item
Level 3
Reload in various situations
*Probably the best skill with the "Reload in various situations" effect, that's more or less the reason to use it.

Landing
Easier to take down enemies when jumping down
Level 3
+20% Capacity for all Weapons
*Pretty useless, the only notable effect is to keep you from getting swarmed when jumping levels, but that's pretty unreliable

Maximizer
Level Skills faster
Level 3
+20% improvement for weapon skills
*I don't rip data from files so I'm unsure what the alt effect actually gives I'm assuming it's a multiplicative improvement for weapon based skills since it doesn't seem to increase Bullet Capacity at all, Firerate or Damage when used on it's own. Seems to be an inferior version of Weapon Master's main skill

Friendship
Vitality Recovers when near co-op partner
Level 3
+8% Weapon Damage for all weapons
*Good for small maps when you can stay near your partner if you have trouble staying alive otherwise it provides low effects.

Thunderbolt
Melee attacks deal Electric Damage
Level 3
Melee attacks release AoE Electric Storm
*This is both good and bad Electric Damage hurts parasites quite a bit and the Electrical Storm gives AoE damage, but it can injure your partner and it's got a large radius too so too so it can be pretty annoying. The Electrical Storm can blow up barrels as well.\

Infinity Seven
Infinite Rocket Launcher when using Krauser's Weapon Set, score set to 0
Level 3
Invincibility (Insta-kill attacks still kill you)
*Just plain annoying since you can't tell people to not use it, eliminates the purpose of playing the game entirely.