Cheats are entered on your Mission Replay Board which can be accessed by visiting any Safe House (you can find the Board on the far right side of the Safe House). The Mission Replay Board has a jumbled set of magnetized letters that can be used to arrange all kinds of words – spell out the letters below to input the following cheats:
Weapon cheat 1 – LOADOA
Grants: grenade, nightstick, pistol, minigun, assault, micro smg, stubby shotgun
Weapon cheat 2 – LOADOB
Grants: molotov, teaser, dual pistols, flamethrower, carbine, smg, dual-barrel
Weapon cheat 3 – LOADOC
Grants: mine, chainsaw, revolver, flamethrower, carbine, smg, dual-barrel
Weapon cheat 4 – LOADOD
Grants: flashbang, bat, pistol, rpg, carbine, micro smg, stubby shotgun
You will know you have entered a cheat successfully when all of the magnetized letters go back to their original position on the board and a piece of text appears at the bottom of the screen with the load-out name you selected. Once you exit your safe house, you can switch weapons by pressing the pause button in the upper right hand corner (a screen with all of your current weapons will pop up).
Source: Rockstar Games
Other Cheat Codes:
CASHIN – Grants $10,000 extra cash.
LIFEUP – Refills your life to full.
SHELLY – Refills your armor to full.
TRIPPY – Reveals all drug dealer locations
COPIN – Raises your wanted level by 1 star.
COPOUT – Lowers your wanted level by 1 star.