I'm sure I've made various odd doo dads to fulfill a task here and there, but the only real tool of consequence I've made is a plane to cut out barrel channels. It is NOT pretty, and is, in fact, rather crude. Originally, I had it make an octagon channel, but it was troublesome, and I decided a better way was to cut basically just the bottom flat... a single "tooth". It does well to quickly get some of the bulk of wood out of the way, I can cut it to the depth of the narrowest part of the barrel (and deepen the rest as necessary with a chisel), and chisel out the rest.
I'm sure I used to have a picture, but you know... Photobucket.