Probably the MOST disturbing - as others are just overly weird - was when I was single and picked up this guy that was in town for a convention. He was a very very attractive guy, even though the wedding band he was wearing made me have second thoughts, I still took him home because he seemed highly intelligent and interesting. (And attractive, don't forget that).
So things go like things go when two guys go home together... he was a great kisser (all over) very sensous in bed... so naturally he ends up face down/ass up in the bed with me behind him trying to push his guts up into his lungs. I banged this guy for about 45 mins nonstop before I finally had an orgasm. I honestly thought the condom was going to burst. I wish it had. When I pulled out, he spun around, grabbed my cock, slid the condom off and then held it up and tilted it over his mouth so the cum would run out. When it was empty, then he popped the condom in his mouth like chewing gum and started swirling his tongue around the inside. If that wasn't gross enough, he seemed surprised I wouldn't kiss him afterwards.