Cheat: Golden Gun:
At the pause screen, enter B, Y, A, B, Y
Submitted by – suntansuperman
Unlockable: Arena Mode
Play through the cooperative missions and acquire multiplayer points by completing the optional objectives.

Unlockable: Characters and Bonus Arenas:
Unlock the following by earning the appropriate number of multi player points, earned by completing objectives in co-op mode.
Agent 003: 290 points
Baron Samedi: 50 points
Burn Chamber arena: 370 points
Arena Mode, and Cistern arena: 30 points
Diayato Moscow: 400 points
Egypt Commander: 90 points
Egypt Guard: 180 points
Hezmet Guard: 110 points
Katya Jumpsuit: 320 points
Le Rogue: 260 points
Miss Nagai: 450 points
Moscow Guard: 230 points
Mya: 130 points
Odd Job: 70 points
Serena: 350 points
Serena: 430 points
South Commander: 210 points
Test Lab arena: 160 points

Unlockable: Cheats:
Unlock the following by earning the appropriate number of Platinum Medals, earned by completing objectives in single player mode.
All Weapons: 17 Platinum Medals
Cloak: 13 Platinum Medals
Double Ammo: 7 Platinum Medals
Double Damage: 9 Platinum Medals
Full Ammo: 11 Platinum Medals
Full Battery: 15 Platinum Medals
Golden Gun: 1 Platinum Medal
Improved Battery: 5 Platinum Medals
Improved Traction: 3 Platinum Medals
Platinum Gun: 27 Platinum Medals
Slow Motion Driving: 25 Platinum Medals
Unlimited Ammo: 23 Platinum Medals
Unlimited Battery: 19 Platinum Medals

Hint: Loads of Tips:
1) Crouching raises the chance of you not getting hit significantly.
2) Always look for available cover at all times.
3) The Q Spider can unlock secret areas and items by crawling through open spaces and scouting.
4) Never charge into a open space without an automatic gun and a lot of ammo.
5) Missiles are very easy to waste and can