I am now physically incapable of doing "vanilla" taunts in TF2. I am forever obliged to spin the minigun, play the flamethrower, spin the wrench, wave with the machete, play the medigun, ride the bat, drink from the grenade launcher, fence with the sapper and beat myself over the head with the rocket launcher.
mind you, it puts the fear of God into some people when playing on Dustbowl if they see a Heavy stroll up, spin his minigun on one finger and exclaim "You! Yes, YOU! You are DEAD!"
what else...?
here's one: I can never, EVER bring myself to do something in a game that offends my moral code. For this reason, I will never the the Dark Brotherhood missions in Oblivion, gain many Renegade points in Mass Effect, use Dark Side powers in a Star Wars game. If we're using the DnD system of morality, then I am never anything other than Lawful Good, 100% of the time.
I'm told that I'm missing out on a lot of good stuff, but I don't care.