In the safehouse there is a Mission Replay Board. Access it and you'll see magnetic letters which you can use to spell out cheat codes. Enter the following codes for the desired effect:

• LOADOA - Weapon cheat 1 (grenade, nightstick, pistol, minigun, assault, micro smg, stubby shotgun)
• LOADOB - Weapon cheat 2 (molotov, teaser, dual pistols, flamethrower, carbine, smg, dual-barrel)
• LOADOC - Weapon cheat 3 (mine, chainsaw, revolver, flamethrower, carbine, smg, dual-barrel)
• LOADOD - Weapon cheat 4 (flashbang, bat, pistol, rpg, carbine, micro smg, stubby shotgun)
• CASHIN - Grants $10,000 extra cash
• LIFEUP - Refills your life to full
• SHELLY - Refills your armor to full
• COPIN - Raises your wanted level by 1 star
• COPOUT - Lowers your wanted level by 1 star
• TRIPPY - ???