Kimball-Midwest Penetrating Oil. Smells like cherries, works like nothing you've ever seen. I blew up the front end in my old mud racing truck once, in the process of taking that apart, I had to remove the spindles. The first one I had to ram with a forklift to remove. The second one got a little spray of the Kimball-Midwest stuff, it came off with a couple light taps from a 16 ounce hammer. The stuff is magic in a can.
In this field, anything I've snapped off, I've just put another screw in right on top of it. I only do residential though.