GameCube
CleanRip
CleanRip is the premier GameCube disc-to-SD (including SD2SP2) imager, with a simple step-by-step UI and hash checking.
Just extract the program anywhere on your FAT32 SD card or other homebrew source, along with the Redump database (gc.dat) in the root, run it, and follow the instructions!
Swiss
While less ideal for this purpose, Swiss (with file management enabled) can be used to copy and paste the full disc image (which is displayed in the disc's root while browsing it) to any device which Swiss can write.
Game Boy Interface (GBI)
If you have a Game Boy Player, you have the option to dump GBA games and saves. See this page for more information.
Wii
CleanRip is also available for the Wii, adding USB storage support, online database updates, BCA dumping, and unsurprisingly Wii disc support. Of course, for GC disc support, a compatible optical drive is needed.
PC
OmniDrive is a custom firmware for MediaTek MT1959-based Blu-ray drives developed by RibShark. It allows for dumping of various game discs that were not previously supported by other drives; that includes RAW reading of GameCube and Wii game discs.
RawDump is a program that leverages the ability of a few Hitachi/LG DVD drives to read the low level format of Wii/Gamecube not-exactly-DVDs.