I usually use .45, on smaller varmints. But my cousin did bring his 9mm a couple times. To save myself some typing, I'll just copy and paste part of a thread from my coon hunting page.
"...So, my cousin laid flat on his belly about 2 feet from the mouth of the pipe, and got out his Ruger 9mm (loaded with hardball) while I shined my light for him. When he shot, the coon moved, so he shot again. And again. The coon kept running right toward us, and as he got closer, my cousin fired faster & faster. By the time the coon was only like 4 feet away, he was reacting with every hit, and my cousin must have pumped a half dozen rounds into him those last few feet. (in addition to the several rounds he fired while the coon was still further up the pipe) But Mr. Coon kept coming without slowing down substantially, and finally came out right in front of us. I think we both jumped up at about that time, or maybe I jumped up first. Things happened so quick I don't remember. Anyway, once the coon hit the ground, he tried running to the east, and my cousin kept putting bullets through him in rapid succession. By now, I had drawn my Kimber and joined the foray. By the time the coon had gone two feet, I shot him 8 times, and my cousin finished emptying his 15 round mag, finally stopping the coon. It took us a moment to calm down, as it was a little exciting to have an angry coon coming at us only 2 feet away, and no way to quickly get out of his way since we were on the ground. We examined the carcass, and it was riddled with holes, including plenty that had to have happened while it was still coming at us in the pipe. One 9mm bullet had caught him just beneath the left eye; another solid hit in the right cheek area, a few in his chest, one shattered front leg, etc. I was actually very surprised that the head shots didn't stop him. I thought even though they missed the brain, the shock transmitted through the bone should have been enough, but I was wrong...."