Perfect Dark Zero

Cheats

Unlockable: Dark Agent
Finish the game in Perfect Agent mode.
Unlockable: CMP-150
Pick itup in Sewer Retrieval, and finish the level with it.
Unlockable: Combat Shield
Pick it up in Trinity Infiltraiton and finish the level with it.
Unlockable: DEF-12 Shotgun
Pick itup in Nightclub Stakeout, and finish the level with it.

Hints

Hint: Zhang Li Boss Tip
An easy sure-fire way to whack this guy is to take a DEF-12 shotgun and any other weapon that is fairly accurate at long distances (any assault rifle or sniper rifle). Zhang Li will dance around the arena and rain on Jo's pretty young butt with death plasma. Evade the shots using Jo's dodge and when you have a clear shot, feel free to shoot back but only if you are sure of a hit.

Damaging the boss enough prompts a shift in attack pattern, and Zhang will hurl obstacles that are diffult to dodge due to the size involved. Simply go to the far end of the platform when Zhang is lifting the object and run (normally) to the other end when the object is thrown.

Continue the attack on Zhang and this prompts him to jump down to Jo's level and attack with the ViBlade. To counter this, dodge and Zhang will falter, dropping the weapon. Normally, you'd take the sword and hack, but it is better to shoot him full on with a double blast from the DEF-12. Zhang will begin his regeneration sequence once he jump back up. Shoot him with the long range weapon to stop his recovery process and Zhang falls back into the ring. Now take the ViBlade and start the hacking and it should be able to finish him off (or at least do serious damage) before he repeats his pattern.
Hint: HAWK Shield On Vehicle
Jo must have the Hawk weapon unlocked for those vehicle stages. Include it in her kit and head for the vehicle. Stand next to the vehicle and throw the HAWK weapon as far out as possible. Before it returns, board the vehicle and when the HAWK returns to Jo's atavism, pressing RB will activate the ballistic shield while Jo is riding.
Glitch: Friendly Fire Off (Ranked Matches)
When creating a ranked game select deathmatch "dark-ops". When the scenerio is highlighted hold LEFT on the D-Pad while pressing GREEN. Cycle through until Eradication is showing again. Friendly fire should now be off. (Unverified)