Once a guy had beaten me pretty badly in a blitz game, and proceeded to insult me. I challenged him again, but this time I came out on top. I kept his king to the a file while I proceeded to get 4 queens :P.
On a side note, I later apologized as did he.
Does your doug bite?
Does your doug bite?
No.
(Proceeds to pet dog and gets chewed up).
I thought you said your dog does not bite!
That is not my dog.
Well this isn't chess but in jujutsu- I pinned and tied up a jerk with his own obi(belt) and left him lying in the foyer of my dojo for about two hours. he had threatened to "knock my wife the f**k out." The pizza delivery guy found it hilarious as this guy was a known butthead of the town. He just stepped over him with the pepperonni pie. I never saw that jerk again.
What's the most unsportsmanlike thing you've ever done to an opponent?
Mine was on Yahoo Chess, and I beat my opponent in 18 moves, and I rubbed it in his face. But it was because he had called me stupid and dumb beforehand, so I felt a need to say, "NOW who's stupid and dumb?" to him.