It's been a while since I was trolling for import suggestions...but unlike the PS1 and Saturn, the GBA is new enough that there isn't a preponderance of information out on the net about the games.
On a side note, I love my little GBA, being at college and not willing to risk my PS1 or Saturn on retarded roommates its the only system I can really have imports lying around for.
So aside from ye olde standards:
Boulder Dash EX
Bubble Bobble Old & New
Elevator Action Old & New
Kuri Kuri Kururin
Mr. Driller 2/Ace
More specifically, has anyone played Black/Matrix for the GBA? I almost picked up a copy on ebay last week, but it was most assuredly a pirate copy. Damn HK. And Hajime no Ippo - Another Treasure game, similar to Punch Out I assume? Any good?