I would love a good inexpensive sheet metal brake, shear and slip roller combo.
A leather bag filled with lead shot. I used a leg cut from ampair of Levis filled with sand for a while. Have the duct tape handy as you will make holes in the denim that will leak sand.
A piece or small leaf spring can be heated and bent, then polished into a slapper.
Look up planishing hammers. I don't know where to get them as I got mine free from watch manufacturers. A bit small but work well on thin aluminum.
I have dreams of making an aluminum roadster body. The swoopy lines kind, not the T bucket kind. Powered by a tiny V8 or a 2.5+ liter 4 banger. I want the body thin enough that it can be dented by pushing it. I guess in a sadist at heart.