Nov 2004 flight on UA SYD-LAX, the guy in front of us in C, main deck had absolutely incredible BO. It permeated the cabin. The guy's intitial seatmate changed seats to the opposite side. There were no other empty seats. A serious impediment to the quality of the flight.

Better than a clothespin is a surgical mask with a few drops of spirit of peppermint (re-apply as needed) over the nose. At the time, I thought about bringing these items along for long flights, but I guess I never got around to acquiring them. Maybe now I'll motivate.