i used a c-clamp with a socket over the head and just tightened it down and hit it with a hammer a couple times

 

cut off the bolt and head, then drilled a couple small holes on one side and was able to pull it out with pliers. other side i drilled out which was how we discovered it was pressed in...that took quite a while tho

 

A friend at work told me today that he's gotten a couple out with an air hammer.

 

watched a guy do this just this past weekend. used a air hammer with a punch and they popped right out.