Word of advise, make sure you check the laser, cause those thigns go bad. they're not hard to replace really (both from the money standpoint and the installation, if you know what you're doing) but just saying.
OT:
Battalion Wars
Pikmin (1 and 2)
SSBM (its obligatory)
I found Custom Robo to be rather good, if you can get past the story and its generic-ness
Army Men RTS (say what you want, I thought it was fun for an RTS)
Alien Hominid was supposed to be good, and my friend said it was, so if that means anyhting to you.
RE4 (yes, RE4 came out on the gamecube. it came out on the gamecube first. Get it, its good, even if it is the gamecube)
If your a pokemon fan, XD was... alright. though i always see it as Pokemon Laughing face now (which is really enjoyment on its own right).
Fire Emblem: Path of Radiance
HP: quidditch world cup was surprisingly fun to be honestly. I enjoyed it probably more then any of real sports game on the Jesus lunch box
Aquaman: battle for atlantis Joking. Seriously, dont buy it. its horrible beyond worlds
Killer7
Midway Arcade treasures (god I loved it. Rampart, Smash TV, Rampage, Sinistar, Joust, Marble Madness, ugh, enough cant be said for how good this game was and how much I played it).
Rouge Squadron 2 was really good (I thought three was kinda shaky, but then again, I was playing 2 more, so I probably just couldnt get past how I didnt need 3 cause 2 seemed perfect)
the Star Fox games are oka, hit and miss I suppose.
If you're into it, YGO Falsebound Kingdom was supposed to be amazing (sadly I missed out, though dont plan on getting new and getting hte cards, its rather unlikely)
and I think one of the tony hawk games was supposed to be good, but i dont know which, cause i just dont carea bout that game series.
...
And of course you have to get the <url=http://en.wikipedia.org/wiki/Game_Boy_Player>GBA attachment to the bottom, cause that opens up the GBA catalog and some of the games work in conjunction with each other, while others can just be played on TV, which is fun for Pokemon games to be on a bigger screen, and Kirby" nightmare in dreamland.