The best would probably be the Gameboy player for Gamecube. In one fell swoop, a player suddenly had a system that could play four console's (three handhelds and one home) worth of games... and without having to re-buy them! lol
But my favorite will always be the Sega CD. I know how people felt about it, and continue to feel about it, but I got one when I was young and they were new and to this day, nothing has managed to immerse me in a game quite like those FMV games. When I played Night Trap, I genuinely felt as if I were there, attempting to save those girls. It was really something.







