Mad Cows: Complete all three shotgun challenges with a "Gold" rank.
Nuclear Bomb: To unlock the Nuclear Bomb, complete all ten deathmatch
challenges. If it does not work with all bronzes, try to get silvers and
golds.
Teleporting: In levels where there are objects floating in the air, if
you teleport onto them sideways, there is a chance that you will actually
teleport inside the object. This is especially true for the green air
ships.
Level generator: Not only can you type in numbers to generate levels, but
you can also type in words and it will convert it for you.