I was at Hastings the other night, looking for a keychain that someone at work told me I would like (he's a gamer too). I went and found said keychain, and bought it.
I forget what the proper name of the keychain is, but there are six buttons on it, and each one makes a sound/music from the 1985 game (ie: Super Mario Brothers).
Here's a picture of the back of the packaging. I would show you the front, but I ripped apart Bowser and Toad trying to get the plastic off the front (the front and back look more-or-less the same, anyway)..