I recently made a neat little sap-ish sort of thing. It's basicly a lead bar that I bent into a hairpin shape, and then filled in the "eye" and soldered down the middle. I rubberized it with black tool-dip.
It's maybe six inches long, by .75 inches wide, by .5 inches thick. Flares out to maybe 1.75 inches at the "head". Weighs about 18 ounces.
I gave myself an experimental thump with it once, not too hard. Will NOT do that again.
Good for all manners of pummeling; you can use either end, use it as a fist load, hammer strike. I need to put some sort of strap or thong on it, though.