Nintendo Gamecube USA Missing
From Redump Wiki
(Almost) all USA GameCube games that were sold normally in stores are believed to be dumped. Additional versions may exist (ex. version 1.00 vs. version 1.01). Todo: crossreference with this list for discs / versions that are known to exist.
Possible Game Revisions
Unknown if these revisions exist. No 1.00 in redump for these titles:
Batman: Dark Tomorrow Bionicle Heroes Dance Dance Revolution: Mario Mix Disney's Hide & Sneak DreamWorks Madagascar Egg Mania: Eggstreme Madness Game Boy Player Start-Up Disc (Have 1.02 and 1.03) Harry Potter and the Sorcerer's Stone Hot Wheels: World Race Killer 7 (2 Discs) Mario Party 7 Mega Man Anniversary Collection Nickelodeon SpongeBob SquarePants: The Movie Odama Pokémon Box: Ruby & Sapphire Serious Sam: Next Encounter Tetris Worlds Tom Clancy's Splinter Cell: Pandora Tomorrow World Series of Poker
Official Application Discs
Aging Test For Production. try59 (maybe there are other versions?) Memory Card Tool Read Check Program [DL-DOL-022E-JPN] 
Properly dumping unlicensed discs is difficult, or perhaps impossible, depending on the disc and the technical skill of the end-user. For more information, see this thread on GC-forever.com.
There might be a disc for each version (1.00, 1.01, ... 1.20, if not more, because of 1.14a-1.14c). The following definitely exist, if scene releases are trustworthy.
Action Replay 1.06 Action Replay 1.08 Action Replay 1.09 Action Replay 1.14a Action Replay 1.14b Action Replay 1.14c Action Replay 1.18  Action Replay 1.20 (Works on all Wiis) (No code entry function) Action Replay Max
Produced by Datel. Some are called "Action Replay Ultimate Codes:", others are called "Ultimate Codes".
Action Replay Ultimate Codes MAX PACK: Mario Kart Double Dash, Mario Party 4 & 5, Mario Sunshine, Mario Golf Animal Crossing Enter The Matrix Final Fantasy - Crystal Chronicles Mario Kart - Double Dash!! Metal Gear Solid - The Twin Snakes (never released?) Metroid Prime The Legend Of Zelda - Twilight Princess The Legend of Zelda - The Wind Waker Wario World
Hopefully not updated as frequently as the Action Replay discs. The exact number of versions is not known.