This one's pretty fun too, along with a decent paintjob. My friend wanted a gun similar to my 4th of July PB gun, and was going to buy one from me for $40. Instead, I built him this one, for $20.
2" Chamber, 3/4" barrel, 2 sparks, makes a very high pitched squeak when shot, probably from the expanding gases forcing themselves through a tiny hole in one of the solvent welds. The weren't perfect, because they're 1 1/4" fittings sleeved inside 2" Sch 40 PVC, but who cares.
Another cheap gun
The wires are stickin' out, and so are the screws, but we just think of them as sights. 
The handle is very comfortable, firing from the shoulder, and you can also fire from the hip comfortably by flipping the gun upside down.
The handle is very comfortable, firing from the shoulder, and you can also fire from the hip comfortably by flipping the gun upside down.