Key The Thief
Gundamu
What about a clockwork sword? It would be a large sword with a bunch of gears on it.

... wait. I know steampunk is fantasy, but why in the blue hell would someone make a clockwork SWORD? Swords are already in fine use, they wouldn't need to waste materials on faffing it up.
Now clockwork machinated weapons makes more sense, like in Girl Genius. Yes, I present unto you, the reader of this post, a brilliantly written and beautifully drawn steampunk webcomic, completely free to read, with tons of examples of steampulp/punk workings.
I think you guys would like this very much :D
A lot of reasons. In my favorite Steampunk Fantasy game, there were two major examples of this; The Clockwork Dagger and the Electrified Sword. The former was a dagger which reacted to the pressure of being jammed into something by pumping the blade in even deeper, causing much more damage than a blade alone, and the latter was a blade which had been fitted with electrical equipment, and had had its handle insulated (I imagine). The sword gave electrical damage. Of course one could simply do that with magic, but they could also do it with science, so why the feck not?