Gamecube is my most beloved console! I have a lot of games I love on GC but these are probably my top ones.
Paper Mario Thousand year door: I loved Paper Mario for 64 so the GC Paper Mario was just as great to me! Lovely cast of characters and settings.
Baten Kaitos 1 and 2, the first one having a twist that I at the time never experienced in a game before and I was so stunned by it. The games themselves are just overall wonderful and colorful RPGs with great music and are super underrated. Planning on buying the remaster soon and replaying it!
Windwaker: My first zelda game I played on my own. Despite the artstyle this game did scare me quite a bit as a kid and it took a while for me to complete it because of that. But it was a fun world to play around in and is in my top 3 zelda games.
Honourable mentions: Super mario sunshine, Mario kart doubledash, Super Smash bros, Tales of Symphonia, Skies of Arcadia, Metroid Prime and Harvest moon a wonderful life.