Infinite health and ammo:
 press and hold right and left trigger
 then press left and right thumbstick and hold
 quickly press white, black,black, white, white, black

This code can be entered at any time during gameplay, just hit the back button which will take you back to the menu screen then enter code
next there will be an option "cheat"

Get all weapons:
Complete game in easy or hard mode
you will then get two more difficulty settings and in "cheats" menu you will have get all weapons option.