What are some GOOD single & multiplayer games for the gamecube. Im buying one soon so I need to know good games. I was thinking I may buy PSO III for I LOVED the first 2 but I need your help.

EDIT I have the following
PSO I-II
NFSU
Metroid Prime
True Crimes
Sonic DX
Sonic Adventure II Battle
F-Zero
Megaman NT
..::*I think thats about It*::>>

PS. What are good PC FREE!!! multiplayer games