A couple of people here have already mentioned my favorite tactic for dealing with snipers. I usually fire a couple of rockets at them to distract them, rocket jump to them, pull out the shovel in the air, and try to melee them when I get to them.
My most epic? I was on 2fort and had a medic with me. We came in the front door and went right. I killed one guy, was working on the second guy and the medic popped the uber. I killed the second guy, switched to my shotgun, killed another guy in the courtyard with my shotty. I moved on to another guy, ran out of ammo, and switched to the shovel. In the end, we both died, but I managed to shovel 1 before the uber ran out and 2 more after the uber ran out. It was one of my more epic runs.