The Georgia one last year had you run for a 1/2 mile-ish, then walk chest deep through a river, jump some hurdles, climb a cargo net, crawl thru long barrels, run up a part of the mountain, crawl under barb wire in the mud, and jump over knee-high fire. And a few other things. When you finish, you can go get a beer and a turkey leg. People dress up all crazy. It's quite awesome.
ETA: You're also encouraged to wear a beard.
ETA: The Georgia run is officially listed at 3.02miles.