I've got a few...
1. Got drunk and passed out in an overly comfortable bed, missed my alarm/forgot to set it, whatever, missed my 7am departure.
2. Was sick, set like 6 alarms to make sure I'd wake up to make my 22:00 departure, sickness took hold of me I guess cuz I woke up at 3am to puke and realized what time it was. Probably better off not flying, but it cost me a lil chunk of change to fix that.
3. Sleeping at the gate standby for a 6am flight after being out all night, gate agent had to wake me up and said "I assumed you were ______ since you're the only one at the gate". ...I'm starting to see a trend here lol.
4. Twice I've taken the wrong hotel shuttle because there was 2 of the same brand.
My best story though didn't even happen to me, but I was the one who caught it.
Drinking at a friends house a day before their departure to SE Asia (I wasn't going) Tuesday night, we're having a good time, as an airline employee/nerd I asked who they were flying...no one knew...asked them what their route was, they also didn't know. So I said "well ... time are you leaving at least, then I can guess since I work there". I was handed one of their tickets, BR flight from YVR-TPE...departure time 02:15.
"Guys, this flight leaves at 2:15"
"yea, so we're prolly gonna leave the house around 10:15 tomorrow morning and pick up everyone"
"No...2:15 AM you geniuses."
"What? No, no flights leave then that's crazy"
"Guys, I work at YVR, airlines write their times in 24 hour clocks, I promise you, this flight leaves 'TONIGHT' at 2:15 am"
*Mad scramble ensues* already like 22:00 the night before and they hadn't packed. Luckily they weren't hammered and they all managed to get packed and to the airport on time.