Hmm...
(R4 Revolution - is/was my first flashcard, gave it to a friend after his M3Real died)
Acekard 2.1 - simply because of the awesome AKAIO
Supercard DS Two - because of the GBA and SNES emulators, also because of its AAP feature (which was superior back then)
Cyclo DS iEvolution - because I thought it couldn't hurt to get a DSi Flashcard
R4i Platinum RTS something - it came with my Cyclo iEvolution
(EZ Flash V 3in1 - no DS flashcard, but wth
- got it because of its RAM (for SnemulDS and Opera DS), but mostly because of GBA ROMs; it's just more fun than playing on an emulator)
Amazekard - well, it looked interesting
EZ-Flash Vi - because I thought, it still got its GBA cheat function, combined with the 3in1
iSmart MM - because of iSmartLinux and its emulators (although they are pretty slow because they are kinda emulated in an "emulator", it was fun to play Breath of Fire 3 on DS
)
I think that's all...