Prince of Persia

Start Prince of Persia by typing in  
"prince megahit" and the following 
"bonus keys" suddenly become available:

K   Kills all enemies on the screen.
R   Resurrects you where you last died.
+   Increase time left.
-   Decrease time left.

Shift-L   Warps you to next level.
Shift-T   Gives you an extra life.
Shift-S   Heals a lost life.
Shift-W   Allows you to float down long drops.
Shift-N   Look at screen below the current one.
Shift-U   Look at screen above the current one.
Shift-H   Look at screen to the left of current one.
Shift-J   Look at screen to the right of current one.
Shift-B   Blocks out non-animated objects.
Shift-I   Inverts the screen.