[JoJo Gunn]

A couple have mentioned the "air blaster" guns. Wham-O made a pistol sized one, but I knew a kid who had one made like a bazooka. Had a red handle to pump it up with. Really loud. I was jealous of him, naturally.

[Merdoug]

I had a blue and white one, like the one pictured and also a bazooka-type (the trigger didn't work, but I could still get it to go off by pulling the handle). I got them out of the atic a couple of years ago and sold them on ebay. The bazooka went for almost 100.00 if I remember right.