All Weapons from Brandon
To get all weapons press start during the game and press z,x,x,z,y,z,y,x, and y.
Then you should have all weapons, keys, and items.

God Mode from Brandon
Press start during the game and press x,z,z,x,y,x,y,z, and y. That will give your
guy unlimited health.

Level select from Brandon
At Main options screen press x,y,z,z,y,x,y,z, and y. If right you will see level
select in blue words at bottom of the screen.