3. Kill The End With Time Travel - Metal Gear Solid 3: Snake Eater
How It's Activated: Once you've reached the boss fight against The End, save your game and then go to the PS2's hardware settings. Move the clock forward at least a week, and then re-load your saved game.
What It Does: The End is one of the most notorious boss fights in the history of gaming, due to his sneaky nature and the fact that if you're tranquilised by him, you will have to repeat a significant portion of the battle again. It took me well over an hour to defeat The End the first time I beat him, but using this cheat, you can do it inside of around three minutes. Reloading the saved game "a week later" will cause The End, the notoriously dedicated hunter, to have died of old age waiting for you, a concession for players who got stuck, yet one that will also tease them for their failure to take the old guy down.