2006 - Left my backpack inside the cab in Cairo (passport / ticket / $$ / camera / binoculars) and merrily walked away without realizing the fact. The cab driver was frantically chasing me down the crowded sidewalks to return me my bag after couple of minutes!
2007 - about to fly to US for first time - left home and realized in a minute that I have left my I-129 at home, without which it shall be impossible to get in to US. U turn and got the document. Relief!
2012 - Flying MDW-EWR on WN on an award ticket that warrants driving down from Milwaukee. Normally it takes me 2.5 - 3 hours in traffic. took me 4.5 hours that day. The door closed when I reached the counter with shoes in my hand. That was the last flight for EWR for that day. Requested to be rebooked on a LGA flight after 30 mins - and got a seat after being standby # 2. People who were supposed to pick me up were having an evening out in NYC - so it was even easier for them.
2012 - Miscalculated the drive time from my relatives place near Philly to PHL for PHL-ORD. Again reached the gate with the doors closing on my face. Rebooked on the next flight couple of hours later.