Normally we ignore "steampunk" news because it has nothing to do with real, actual steampunk and more to do with some bloke attaching nonfunctional brass tubing to his PC, but in this case these guns actually shoot something.
The blunderbuss, above, shoots rubber balls. Cool, I suppose...But! It also shoots them at such a velocity that they can penetrate cardboard at a respectable distance:
The other rifle, Black Betty shoots ping pong balls and confetti paper, the latter of which can be lit up to make a flame thrower of sorts: