I once started singing that Bill Cosby remix spontaneously. That got some looks.
I also remember that I'd been playing Cossacks: Napoleanic Wars for a while and me and my friend had asked Spain for an alliance. They politely declined, sparking off a war and utmost hatred of them for eternity. Spain was once mentioned in one of my history classes and I uttered out loud, in a gutteral Gravemindish voice: "Spain... my nemesis."
My friend and I have also shouted, in Demoman voice: "Ka-boooooooooom!"