Dell QuietKey.
No questions asked, it's the best keyboard I've ever used. I've had one since I started using computers, and anytime I've used another, it's just been inferior in overall feel. It doesn't have the bells and whistles of newer keyboards, but it's perfect for what it's designed to do.
http://www.directron.com/dellkb1.html
That's the newest version of Dell's QuietKey. Directron has them for $6.00. My friend got one on sale for like $2.99.
When it comes to keyboards, I can't play games or even type worth a shit unless I'm using one of these. If you buy one, you won't be disappointed. Hell, it's worth getting one just to try out since they're $6.00.
-Lasereth