The Mavs throw a charity Christmas party at the DFW area Gameworks every season. This year the invitees were all participants in the Special Olympics. As always Dirk was in attendance and spent a lot of time playing the guests in various videogames. And he wasn't about to lose - much less let someone win.
Also, there have been a lot of funny pictures (1 | 2) of Dirk on the internet and this one of Dirk playing Dance Dance Revolution is right up there for me.