I rolled up behind three of the club riders who were standing on the trail, looking at a bike. One of them had crashed, and the derailleur hanger on his bike was bent inward, which forced the derailleur into the spokes. Luckily, none of the spokes were broken.
I pulled out my CoolTool, and removed the derailleur from the bike. Then, using the adjustable wrench built into the tool, I bent the hanger back to its (approximate) correct position. After I replaced the derailleur, I had the rider test it out by riding up the trail and sifting through the gears. I had luckily gotten the position very close to right, and the indexing was working, so we continued on.
Soon, we came upon another club member. He had a flat tire. Three or four minutes later, I was through replacing his tube, and we soldiered on.
Along the way, we encountered another flat tire, and a loose headset. Both were quickly dispatched.
As we rolled into the trailhead parking lot, Bill (who had ridden ahead with the fast guys) enthused, "What a great ride! No mechanicals!"
There are never any mechanicals, off the front...