Any of them, since I have one of each LOL. Not many people have several units of the same system.
I have an Atari 2600 and a Sega Master System. Of course I don't keep the original packaging of either, and I think at least one of the controllers of the SMS was destroyed (by my sister). But in compensation Odin bestowed upon me the Sega Control Stick and the Light Phaser:
http://www.smstributes.co.uk/gethwin...?hardwareid=21
http://www.smstributes.co.uk/gethwin...?hardwareid=20
The blasted cat chewed the stick's cable in two but I was able to repair it back then.
I never use them, they're gathering dust in my junk room, it's more convenient to use emulators in my PC, even with the systems and games that I own.