Make three new character profiles with the following names:

XaX 1985
QA Tester
Dentist Guba

At any time during the game hold both the left trigger and white button to make the cheat menu appear. While there're depressed use up/down on the D-pad to select cheat and press right to activate it.

Cheats are context sensitive. Some only work in-game yet others only during map editing and so forth.

Thanks also to Recoill and maxqubit.