Reccomend me some Gamecube games!

[The Inquisitive Mug]

Metroid Prime, I cannot stress this enough. It's one of the most spectacular games I've ever played. It doesn't matter how deep I am into any other game, if I start playing Metroid Prime again I will not be able to stop.

The Legend of Zelda: The Wind Waker and Soul Calibur II are similarly amazing. I also enjoyed Resident Evil 4 and Viewtiful Jow.

 

[OncomingTraffic]

The obvious ones have probably all been mentioned, so I recommend Geist.
It's a very original shooter where you become a ghost and possess a variety of objects and people.
It also has a few puzzles, but they fit in with the dark atmosphere.
You could find it for around $10, so give it try, if you want to that is.

(You said "feasibly buy", so I didn't say Skies of Arcadia Legends, but you never know.)

 

[Scarim Coral]

Since no one mention it (and shame on you), I highly recommend Gotcha Force. It's such an underrated game and it's a rare gem too!

Also picked up Metal Arms: Glitch in the System and Time Splitters 2 and 3.

 

[EbonBehelit]

Well, here's my GCN collection - I consider every game on it to be worth buying at the very least:

Super Smash Bros. Melee
Metroid Prime
Metroid Prime 2: Echoes
The Legend of Zelda: Wind Waker
The Legend of Zelda: Ocarina of Time + Master Quest
Tales of Symphonia
Paper Mario: The Thousand Year Door
Super Monkey Ball
Super Monkey Ball 2
Timesplitters 2
F-Zero GX
Sonic Adventure 2: Battle
Viewtiful Joe
Viewtiful Joe 2
Fire Emblem: Path of Radiance
Ikagura
Product No. 3
Skies of Arcadia: Legends
Metal Gear Solid: The Twin Snakes
Resident Evil 0
Resident Evil
Resident Evil 2
Resident Evil 3: Nemesis
Resident Evil 4
Eternal Darkness: Sanity's Requiem
Naruto: Gekitou Ninja Taisen 4
Star Wars: Rogue Leader
Star Wars Rogue Squadron 3: Rebel Strike
Luigi's Mansion
Mario Kart: Double Dash!!
Bomberman Generation
Pikmin
Pikmin 2
Rayman 3: Hoodlum Havoc
Prince of Persia: The Sands of Time
Mario Party 4
Mario Party 5
Wario Ware, Inc.: Mega Party Game$
Burnout 2

Don't worry, I know I'm missing a fair few - got a list for those ones too. Feel free to point out which ones I'm missing though, both to fill potential holes in my list, and for the sake of completeness for the OP.

 

[MangaVally]

Skies of Arcadia: Legends is an amazing game that everyone should play. Also their are a few other great ones, Like the Metroid Primes and Paper Mario and the Pikmins

 

[Dark5tar1]

Wind Waker
Twilight Princess
NFS Underground 1 & 2
Viewtiful Joe
Splinter Cell
Billy Hatcher
Super Smash Bros Melee
Any SSX game
Any TH game
F Zero GX
Killer7
MGS Twin Snakes
Paper Mario: The Thousand Year Door
Star Wars Rouge Squadron 3

 

[Terramax]

Stairfax temperatures

Man, I loved that game.

Id recommend Star Fox Assault, if you can afford it and, whilst not a Gamecube exclusive, you NEED either a Cube or xbox copy of Metal Arms: Glitch in the System.