MadStone High gravity
At the main menu, press Down four times, Right, Left, Right, Left.
Low gravity
At the main menu, press Up two times, Left two times, Up two times, Right two times.
Player skulls in Arcade mode
At the difficulty selection menu, press Up, Right, Down, Left, Up, Right, Down, Left.
Savant mode
Select Single Player mode in Arcade mode. Press Down ten times at the difficulty selection screen. The pointer will move underneath the Master difficulty, and the game will start in Savant mode.