My worst were:

SAN-JFK on B6
It was a 6 hour flight and I was stuck in the middle of two guys who talked all night long. I asked them if they wanted to switch seats to be next to each other but surprisingly, they wouldn't.

SFO-LHR on VS
My wife and I had the two middle seats of the middle section of four. Longest flight of my life!!!!!!!!!!!!!!!!!