After playing Super Smash Brothers Brawl at a party in a sound proof room on a projection screen, I've been trying to convince my parents to do the same to one of our unused rooms. Build a "teenage hangout". It will be very hard to convince them to do this, the lower the cost, the better. Is there any cheap tricks do doing this (and still look nice)? Memory foam on the walls? Obviously the screen itself will take the most convincing, but if that fails I'll use our 60in TV (three years of begging at it's finest :D ).
I might even make it into an Instructable.