I got a bunch of GBA games for Christmas while visiting family in Michigan these past few weeks. I figured it'd be rude to lug my PS3 over, so the GBA was a natural choice. I recently picked up Golden Sun and FFVI Advance and then added these gems to my collection: 
 
Street Fighter Alpha 3 
Advance Wars 
Advance Wars 2: Black Hole Rising 
Riviera: The Promised Land 
Wario Land 4 
Yoshi's Island: Super Mario Advance 3 
Mario & Luigi: Super Star Saga 
 
And in addition to that, I also bought a Game Boy Micro. 
 
Now if I could just find Tactics Ogre: Knight of Lodis, WarioWare, Rhythm Tengoku, Metal Slug Advance, and Legend of Zelda: The Minish Cap.  Also, <strike>Super Robot Taisen: Original Generation 2</strike>