All of the following cheats are entered under "Options" -> "Cheat Codes". Single player missions unlocked:
Enter Y, Down, R, Down.
Toggle God mode:
Enter Up, L, X, L.
All ammunition:
Enter Down, Up, Down, Y.
Toggle location stat:
Enter X, Right, L, Left.
Win current match:
Enter L, L, L, Y.
Lose current match:
Enter L, L, L, A.