Tweaking the game

[shinyminidrake]

You have to edit the game files to get the "What have you done achievement" and there are some pretty trivial ways of doing that, such as swapping the existing maps. What are some INTERESTING ways of modifying the game, though? There are some YouTube videos showing how to make you invincible, jump extra high, change eversion level at will... what's the best way you've found to modify it?