Backyard Wrestling: Don't Try This at Home

Cheat Menu
At the main title screen, hold L1 and enter the following: X, Triangle, X, Triangle, Circle.
(Thanks to BigMonster23cu1@aol.com)

Unlock Everything
At the main title screen, hold L1 and enter the following: X, square, triangle, O, X, square, triangle, O.
(Thanks to anditendedwithe@hotmail.com)