Flashcarts are cartridges that has an SD card slot for adding your own games. They are usually unlicensed.
Systems
Flashcarts have been released for the NES, SNES, Sega Genesis, Game Gear, Nintendo 64, Game Boy/Game Boy Color, Nintendo 3DS, and (most commonly) the Nintendo DS.
List of Flashcarts
Here's a list of (almost) all of the flashcarts ever released (as of September 2014):
NES:
- PowerPak
- EverDrive N8
SNES:
- SNES PowerPak
- Super EverDrive
Sega Genesis:
- EverDrive - MD
- Mega EverDrive
Sega Master System:
- Master EverDrive
Sega Game Gear:
- EverDrive - GG
TurboGrafix-16/PC Engine:
- Turbo EverDrive
Nintendo 64:
- EverDrive 64
Game Boy/Game Boy Color:
- EverDrive - GB
- GB Smart Card
Game Boy Advance:
- Smart Card
- EZ Flash IV
- MV Perfect SD
Nintendo DS:
- R4 - Revolution for DS
- DSTwo
- EZ Flash V
- Acekard (2)
- DS-Xtreme
- R4 3DS
- CycloDS Evolution
- Games n' Music
Nintendo 3DS:
- Gateaway