I know a guy like that, but even worse. This guy in a similar position extended his hand (but with him still on the move, like he is resigning), but split second before the opponent took it he said: "Draw?" That was hilarious. The opponent couldn't believe it, and neither did we in the audience   Remark: even if the opponent took the hand the game is not a draw, so people - don't be tempted to do it. It will earn you a bad reputation, which will stick with you for a LONG time (because the story is excellent for retelling). Edit: In your place I would force him to repeat it but more loudly with simple "What? I didn't hear you."

I must say here (with regret) that you have shown extremely bad technique of playing this particular opponent and position. After 40...a5 he can only go between b2 and b3, which is really humiliating. Since he is obviously not going to resign, I would calmly and SLOWLY take his 2 pawns and then use the 4 kingside pawns to resurrect my 2 Bishops, Knight and Queen. The main point is to be very very slow, so everyone in the playing hall has time to see the position. If he quits chess after this then all is well and you have done a favour to everyone.

or instead of 42.a3+ you could mate in two by simply repositioning you knight to d1 d3 or c4, but i agree with Marinvukusic against someone like that make them suffer!