I recently had a stubborn water pump problem, and I thought I'd share what worked for me. I removed the upper and lower timing chain cover and the harmonic balancer to provide a little extra space (I was doing a timing chain job anyways). I put a big pipe wrench on the pump and then a cheater bar on the pipe wrench. Using all the strength I have, I was able to get the pump to turn. It only moved a few degrees at first. After turning it clockwise and counter clockwise many many times, it slowly started to work its way out. It was calcium deposits that had made it stick. Of couse, be careful and don't scratch any mating surfaces while the timing covers are off.