This F4 is alledgedly at 5 feet:
http://www.youtube.com/watch?v=ApM_f-jBlP0

It happens right around 39 seconds. I've also seen a photo of an Su-37 on Airliners.net that was flying at less than 3 feet over the runway. I don't see why pilots attempt to do this stuff though, can you imagine what would have happened if that F4 hit that dirt mound with the people on it?