I like to play TF2 sometimes with Baroque and Classical in the background. Adds an air of importance to everything.
Also, I once played that "Art of War" TF2 theme over a TF2 game. You know the drum-only one, right? You know that epic pause in the middle? Everytime that happened in-game, something epic would happen whilst everything else froze to a halt (cinema style), then the drums would burst back in and everything would carry on.
Whether this happenes by coincidence and I just notice it due to epicness, or it's a conspiracy, who knows!?