All You guys missed my favorite option, and one I've used many times
Grab a dremel or other rotary type tool and cut a nice long slot straight across the head of the bolt.... Then grab the BFS (Big Freaking Screwdriver) and i'm sure you can figure out what to do next
I used this method on an inverse Hex lugnut once... was skeptical of it working, but with my BFS, a pair of good vise grips around the handle, and a 4ft pole over the end of the visegrips, it popped quick
Also, requires the least amount of work....
Later,
Adam
P.S. Don't forget to WD-40 the hell outta that thing first