The name might be crude, but the product is pretty clever. Guitammer's ButtKicker Gamer is a vibrating bass module that puts some thump into your gameplay. The surprisingly heavy ButtKicker device clamps onto your chair, and the included amplifier runs between the ButtKicker and your audio input. When you start playing, the ButtKicker starts jumping, making your seat rock and rumble with every shot and explosion.
Rumble seats are hardly new for gaming; bass-rocking gaming chairs from companies such as Pyramat and D-Box can be had by anyone willing to shell out the cash. They're usually bulky chairs that can't work very well at a desk, though. The ButtKicker Gamer's clamp-on device lets you use your own chair until it shakes apart.
The ButtKicker Gamer is currently available for about $100. Larger, home theater-oriented ButtKicker modules are also available, though they are more expensive and more likely to shake your house to the ground.