Quote Homeboy: The Butt Kicker is a device that connects to your chair and rattles the chair based on low frequency sounds coming out of your sound card. It's basically another form of forcefeedback and works really well. I bought this thing about three years ago for about $60 and never really used it much until I began playing OFF. Let me tell you, when you bring that Spud around for landing and pull the throttle back to idle and the stick and chair are both rumbling, it is a fantastic experience! I wouldn't spend a bunch of money on one of these things but if you can get one for under $100 it's definitely worth it.
I agree Homeboy. I don't have a Buttkicker but I use a gaming chair, much the same thing, and I feel like I'm sitting in my crate feeling the rpms of the engine in my back, butt and legs. I feel archie going off around me too. Just picked up a set of rudder pedals and when I get that sorted out I'll have a very nice virtual cockpit.