In Mass Effect for the PC and Xbox 360, there are a lot of unlockable bonuses and skills you get through various ways.
Unlockable Bonuses:
5% Bonus Weapon Damage – Complete the game twice on any difficulty
5% Exp Bonus – Reach level 50 with a character
10% Exp Bonus – Complete 75% of of the game
10% Hardening Bonus – Complete 75% of the game with Ashley in your squad
10% Health Bonus – Kill 150 organic beings
10% Reduced Cooldown for Barrier and Stasis – Complete 75% of the game with Liara in your squad
10% Reduced Cooldown for Lift and Throw – Complete 75% of the game with Kaiden in your squad
10% Reduced Cooldown for Overload and Damping – Complete 75% of the game with Garrusin in your squad
10% Reduced Cooldown for Sabotage and AI Hacking – Complete 75% of the game with Tali in your squad
10% Shield Bonus – Kill 250 synthetics
10% Shield Bonus – Sustain more shield damage than health damage on one playthrough
25% Marksman Cooldown Bonus – Get 150 kills with the pistol
Regenerate One Health Per Second – Complete 75% of the game with Wrex in your squad
Unlock Spectre Grade Weapons to Buy – Acquire 1,000,000 credits
Unlockable Skills:
Assault Rifle Skill for New Characters – Get 150 kills with the Assault Rifle
Barrier Skill for New Characters – Use Barrier 75 times
Decryption Skill for New Characters – Use Sabotage 75 Times
Electronics Skill for New Characters – Use Overload 75 times
First Aid Skill for New Characters – Use 150 Medi-gel
Hacking Skill for New Characters – Use AI Hacking 75 times
Lift Skill for Non-Biotics – Use Lift 75 times
Medicine Skill for New Characters – Use Neural Hacking 75 times
Shielding Skill for New Characters – Use Dampening 75 times
Shotgun Skill for New Characters – Get 150 kills with shotgun
Singularity skill for New Characters – Use Singularity 75 times
Sniper Rifle Skill for New Characters – Get 150 kills with the sniper rifle
Statis Skill for New Characters Use Statis 75 times
Throw Skill for New Characters Use Throw 75 times
Warp Skill for New Characters Use Warp 75 Times