couple of times ive been that guy once in a game of wfb an opponent who carried rulebooks with him but never seemed to have the one showing the rule that helped you. he'd questioned two rules which I knew the answer to and gotten the shop staff to agree with him when I eventually won I ran around the shop cheering.
then a 40k tourney a gw member of staff was using the new eldar codex which hadn't been released questioned a minor rule again he was wrong but the organiser agreed with him as they were mates the rest of the game I did my best to make sure he didn't enjoy it didn't shake his hand and told him why at the end.
im pretty sporting apart from that I enjoy playing against power gamers as I like working out how to beat them.