My favorite tool is something I just put together myself, about a year and a half ago.
My headset fork crown race setter.






Just a trip to the hardware store for some PVC plumbing items (About 6 bucks worth) and some thick silicone rings (To center the steerer tube in th PVC tube) I salvaged from empty prescription bottles a few years ago.
Works a treat and is now a veteran of five headset race installs it is a surprisingly effective tool that just cost me a few bucks.
The bonus was my Park headset race remover tool fits inside it for storage, so all the headset tools I need are in one place, except for the lock ring wrenches....