I have to say I am really enjoying my Nintendo DS Lite with the M3 Lite addon, the functionality it adds is simply awesome. Check it out.

The second picture is a close-up of the M3 Lite. The The M3 stands for Max Media Movie Player and it is a Slot 2 cartridge for the Nintendo DS Lite. With it, you can add MP3 music, play movie files and even run homebrew software that is released on several sites. Personally I use it to play my favourite anime episodes, as the video quality is fairly decent.
The next release is the R4 which is supposed to be superior in quality, but the M3 will probably remain the market leader for the DS Lite because of its already-extensive features.
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