Only game I remember that has a spaz shotgun other than Vice City is Half-life. It could be a lot of games, though since I think the spaz is a real life weapon. EDIT: Apparently the real life version is called spas and yea, that gun is in a ton of games. Only game that I am sure that called it the spaz was vice city.
Well it would help if you described the game, or gave us something. You cant find a murderer without clues...