Monster House [GBA]

Doom Bringer 3000 DJ's best water gun
Beat Skull's high score of 50,000 in Thou Art Dead to open a passage way to a chest with the Doom Bringer 3000, DJ's best water gun. Can be gotten as soon as you start your second playthrough on the same file.

Doom Bringer 3000
Beat Skull's high score of 50,000 in the Thou Art Dead arcade game.

Hard Mode and Ruby Key
Beat the game once to unlock Hard Mode. You start the game over on the same file and a brass heart is added to the save file.

You also start with a Ruby Key. Needed to unlock the door at the right of the lobby that is said to need a "special key". It leads to a room with an arcade game that you can actually play. It's called "Thou Art Dead". Plays much like the old Castlevania games, except the character looks like a Golden Axe character, and the monsters are different.

Hard Mode - Beat the game once
Ruby Key - Beat the game once