For me it wasn't the BJ in and of itself; but rather the context in which it was performed.
A FWB and I were experimenting a lot with each other; and during one of our sessions anal sex came into play. And just as I was about to bust she pulled away, turned around and finished me off with a BJ. A combination of excitement and surprise at having my first "ass-to-mouth" caused me to nearly have an aneurysm when I came in her mouth.
I did ask her to be my GF after that; but she had squarely placed me in the "friend zone." Maybe for my own good. The song "Super Freak" by Rick James comes to mind: "She's a very kinky girl; the kind you don't take home to Mother."
