Two incidents:

1- Flying SFO-LHR on Virgin Atlantic, I decide to take BART to SFO. Only a carry-on, I've got plenty of time, so no worries right? As the train gets close to Colma everyone hears a loud crash and the train jolts to a stop. Turns out a tree has fallen onto the train! We receive word that the train can't move any more and they need to troubleshoot. Uh oh. About 30 minutes pass and we hear that they plan to shuffle everyone to the cars in front of the damaged ones, drive another train back to us, couple it, and then drag us the rest of the way to the station. We're now at 2 hours before departure. Everyone sits around for another 30 minutes. The power goes out. I begin to doubt that I'm going to make the flight. The rescue train arrives, but they have to drive it at 10mph for safety reasons. I get a cab to SFO from the station and sprint to the check-in desk, get my passport checked, rush through security. Gate area is totally empty but the doors are wide open. Turns out ATC announced a ground stop at the tail end of boarding so they never closed the doors! Whew.

2 - Self-connect XXX-HKG-TPE transferring to Cathay Pacific. I was stupid and forgot to get the connecting boarding pass pre-printed and there's a long line at the transfer desk. It's moving quickly though—and then I get stuck behind some poor guy whose itinerary is obviously three kinds of screwed up. There's only one person manning the transfer desk. The line grows longer and longer. About 40 minutes before my connecting flight, I spy that the immigration queue has completely cleared. I scribble out a landing card and told them that I need to go see the ticketing desk. Thank god they didn't bat an eye. I enter HK for about 10 minutes, get my BP, go back through immigration, and get to my gate about 15 minutes before departure.