Check image
Hint: Cursor Colour
Play the coloured game and pay attention to your reticule. When it shifts colour from white to another colour, you are targeting something interesting:

Red is hostile target.
Blue is a destructable secondary objective.
Black is destructable environment.
Green is a friendly (rare).

Alternates
HQ6G-ZP3B-C5LE-WMXA
EG4P-ZGUJ-6SQJ-3X68
6DEG-7W3X-RKJF-TDF4
3K67-9J5G-NSQH-G49M
3ZEQ-JXH9-TR2H-Y87D

Unlockable (Clearing Modes)
Silver Weapons ... Clear the game on normal or hard and the weapons will be silver with unlimited ammo.
Black Ops Difficulty ... Clear all stages on hard difficulty.

M16A2 ... Clear the game on BlackOps for an M16 w/ URGL attachment.

Unlockable MSAW
Use 5SQQ-STHA-ZFFV-7XEV a profile name (new profile). Note there must be a dash between each set of alphanumerics. Once you confirm the profile name, the game will ask for a 2nd (real) profile name. This code lets you have an MSAW in place of your side arm.

Alternates ... HQ6G-ZP3B-C5LE-WMXA and EG4P-ZGUJ-6SQJ-3X68.

5SQQ-5THA-ZFFV-7XEV
5SQQ-5THA-ZFFV-7XEV

1 hit dead
X up xx down and up

Unlockable MSAW
HQ6G-ZP3B-C5LE-WMXA and EG4P-ZGUJ-6SQJ-3X68

Easy wins!
Get a sniper and a hand gun. Then stay low and spine out the enemy and when they get close use the hand gun!

Head Shots
Head Shots kill quicker

Hint silver weapon
When you complete the game in hard or black opp ure weapons tuen silver with unlimated ammo!

Infinite health
D59B-3Q5Y-6EGDB
V8YT-0V62-2G72B

All ammo and weapons
12352627595