4. Infinite Bullet Time - Max Payne
How It's Activated: On the PC version, you need to access the game console after having started maxpayne.exe with the "-developer" command line. Once the game is loaded, press F12 to access the console, and enter "GetBulletTime" to refill your bullet time meter whenever it runs out. Alternatively, a trainer program can be run in the background which will allow your bullet time meter to stay permanently full without needing to re-input a command line code manually.
What It Does: It makes Max Payne a Helluva lot more fun. While it's already tremendously entertaining to run around with a vast array of weaponry, gunning down goons in slow motion, the game's difficulty comes in rationing out your bullet time and ensuring that you use it at opportune moments to clear large rooms of thugs. If you mistime an attack (such as forgetting to reload before activating bullet time), you can be left extremely vulnerable and find yourself desperately needing painkillers. This cheat allows you to essentially play every gunfight in as much slow motion as you want - Hell, even the whole game if you so wish - giving you more time to react to the enemies and, more importantly, giving you adequate time to line up the perfect, John Woo-inspired kill.