Lockpicking

Increases chance to pick regular (non-electronic) locks. (2)

Hand-to-hand

Increases hand-to-hand attack damage by 45%. (2)

Increased chance to hit in Hand-to-Hand and blunt-weapon attacks by 15% (2)

Increases chance to dodge Hand-to-Hand or Blunt-Weapon attacks by 15%, if you're not armed with a knife. (2)

Electronics

Without this skill, repairing electronic devices takes twice as long. (1)

Same goes for repairing the Robot. (1)

Without this skill, picking electronic lockpicks is twice as hard. (1)

Without this skill, attaching remote detonators to explosives is twice as hard. (1)

Without this skill, planting remote-detonated explosives is 25% harder. (1)

Without this skill, disabling electronic traps is 25% harder. (1)

Without this skill, attaching some electronic items to other items is twice as hard. (1)

Night-Ops

Reduces time required for sleep, as well as the speed at which the character loses fatigue. (2)

Increases vision range at night by 1. (2)

Increases hearing range by 2 at night, and by 1 at any other conditions. (2)

Increases chance to get an interrupt during nighttime. (2)

Throwing

Increases throwing range by 12%. (2)

Increases CTH with thrown weapons by 12%. (2)

Teaching

Increases speed of training militia and other mercs by a certain amount (you can set that amount in Options.INI). (2)

Heavy Weapons

Increases base Chance-to-Hit with Rocket Launchers by 15%. (2)

Increases CTH with launched grenades and other high-angle launchers by 15%. (2)

Auto Weapons

Reduces chance to fire "unwanted" extra bullets in auto mode.(2)

Reduces Auto/Burst penalty for each Auto/Burst bullet, by 50%. Also works with launched-grenade bursts. (2)

Stealthy

Decreases noise created by moving about. (2)

Martial Arts

Reduces time required for sleep, as well as the speed at which the character loses fatigue. (2)

Increases damage in hand-to-hand and blunt-weapon combat by 30%. (2)

Increases chance-to-hit in hand-to-hand and blunt-weapon combat by 30% (2)

Increases chance to dodge knife attack by 10%, if you're also armed with a knife. (2)

Increases chance to dodge knife attack by 15%, if you're not armed with a knife. (2)

Increases chance to dodge Hand-to-Hand or Blunt-Weapon attacks by 30%, if you're not armed with a knife. (2)

Please note: Martial artists do NOT get a damage bonus from Brass Knuckles or other blunt weapons!

Knifing

Increases chance to cause instant death to a target, when using throwing knives and the target can't see the thrower. (2)

Increases chance to hit with knife attacks by 30%. (2)

Increases chance to dodge knife attack by 30%, if you're also armed with a knife. (2)

Increases chance to dodge knife attack by 10%, if you're not armed with a knife. (2)

Increases chance to dodge Hand-to-Hand and Blunt-Weapon attacks by 15%, if you're also armed with a knife. (2)

Professional Sniper

Increases maximum CTH bonus possible with extra aiming by 10 points. The maximum regards the total bonus possible, which is usually achieved only after several right clicks. (2)

Reduces "effective" range to target when calculating CTH, regardless of the weapon used! (2)

Camouflage

Gives 100% Woodland Camo, permanently. (1)

Ambidextrous

Without this skill, you get a -20% penalty to CTH when firing two one-handed weapons. (1)

Source: Headrock at http://www.ja-galaxy-forum.com/board/ubbthreads.php?ubb=showflat&Number=195392&page=1#Post195392