Hi!
What does the Spud Gun do? It has a body count of 0 ! I don't understand how and when it must be played!
AFAICS it is useful for shoot outs (by virtue of being a gun), but that is all.
V.
...or in order to discard a single card 
Yeah, that's pretty much it. It came about because somebody (I don't actually remember who) wanted more Gun cards, but for balance reasons another actual weapon wouldn't work.
Well, that and it's funny to win a shoot-out with a spud gun.