MegaDrive. Don't remember how I got it, I just always had it. I don't play it that often if at all anymore as I prefer the ease of emulating on my HTPC with retroachievements. Even got a nice saturn style fight pad that works great for MD games.
Also the model I have is the region free Asian one even though I live in the UK. I've always had a JP copy of sonic 1 too. No idea how they ended up in my hands.