A card that allows you to play 3DO games on your PC, similar to the NEC PC FX GA. Not a bad idea, retailed for about $50 less than a normal 3DO (when the price finally dropped to something reasonable, that is.) I have heard about some compatibility issues with newer versions of Windows, however there's usually a work around for stuff like this. Pretty useless if you already have a 3DO.
The cool thing about stuff like this is that inquiring minds can hack this and do all kinds of neato stuff with it, like rip 3DO roms, turn it into an el-cheapo development system, etc. The 3DO homebrew scene is pretty usless, which is kind of sad, as in my opinion this is another one of those machines that never reached it's full potential.