Does it count as an OpUp, if it was a bribe to keep me from demanding IDB compensation? If so, USAir, back in the 1990s... very full flight, no checked bag, no status, no online/phone check in back then... checked in a few minutes ahead of the whatever the minimum required was (40 minutes, I think) and discovered they'd already given my seat away.

Initial offer was "it's your fault, you're lucky we're offering you a seat on the next flight," but given that I was on time (by about 2 minutes left) and they were not budging on giving me my seat back, I asked for bump compensation. I was offered a voucher, or an upgrade to domestic F on the flight they'd moved me to. I'd already decided to give up on USAir, so I took the upgrade. If I'd known about the difference between IDB and VDB back then, I'd have held out for cash, but I didn't.

Was also my first flight in any kind of F/J.

First "real" op upgrade, and my only one on AA, was coming back from London at some point in 2003. I'd flown a lot of domestic F on stickers by then, and a tiny handful of J awards/mileage upgrades at that point. Was flying with my wife, on separate itineraries (mine paid, hers award.) I spotted after at check-in that my seat had been moved and was not next to hers any longer but didn't immediately realize where I'd been moved to. When we got to the gate, I asked to get moved back to the original seat next to her, and the gate agent moved her up to J next to me instead.

Score.

I've gotten a couple of op-upgrades on CX; one regional J from HKG-SIN, and a couple HKG-SFO. My wife and I also once got a half-upgrade on JL, from KIX-LAX -- the upper deck J cabin was being run with Y service. Worked for me, the seat is the important part (this also makes me miss the couple of years when every Christmas we'd fly to visit my family through Newark rather than JFK so as to take advantage of the 762-sold-as-2-class flights.)

Not sure what it means that virtually all of my op-ups have been returning to the US, rather than starting from in the US.