A lightgun for the Sega Megadrive (Genesis)
The menacer, like the Super Scope uses infra-red to communicate with a sensor near the TV1. Aside from the demonstration cartridge that came with it, there were two games released for the menacer: Body Count and Terminator 2: Judgement Day. The Menacer's gimmick was that it came with removable parts - The lightgun was pistol shaped (Think of the silenced pistol from Deus Ex), and came with an add-on stock, and binocular sight. The sight could be adjusted to be used with either eye, and each eyepiece could be removed. The menacer takes six(!) AAAs, which don't exactly last long. I would recommend buying rechargables.

1- (I've seen it use the same IR commands as the TV, making the TV change channel whenever a button is pressed)