GameBoy Advance SP

Buy one. In addition, buy a copy of any of the following games.

Castlevania: Aria of Sorrow
Fire Emblem
Golden Sun
Golden Sun: The Lost Age
Harvest Moon: Friends Of Mineral Town
Mario & Luigi: Superstar Saga
Mario Golf: Advance Tour
Metroid: Zero Mission
Metroid Fusion
The Legend of Zelda: A Link To The Past

There's also a very good Grand Theft Auto game that was just recently released on GBA. If you're into GTA, that one will suit your fancy just fine.

Either that or grab some books. I recommend starting up the Dark Tower series by Stephen King. That would keep you busy for weeks.