Zapper

Beat Current Round
Collect 6 eggs.
(Thanks to cyanter@hotmail.com)

Cheats
Collect 100 fireflies in each level.
(Thanks to cyanter@hotmail.com)

Fly
Beat the first world with 400 points.
(Thanks to cyanter@hotmail.com)

Ultimate Weapon
Continue to buy fireflies until you are given the ultimate weapon.
(Thanks to cyanter@hotmail.com)

Unlimited Lives
Pause game play, then hold then hold L and press Up, Up, Up, Left, Left, Right, Left, Right.
(Thanks to cyanter@hotmail.com)

Unlimited Shield
Pause the game, then hold L and press Up, Down, Up, Left, Right, Down, Up
(Thanks to cyanter@hotmail.com)