Stripped the Bolt Head

I usually use a specially designed socket (example of a Canadian Tire set "Extract-it" shown) that grabs a stripped bolt and bites into it when pressure is applied.

In case you have a welder, weld another bolt or nut on to the stripped bolt and use that one to undo it. Apply some nice creeping oil, to loosen things up and some heat from a propane set and go to town LOL