Mechanical Keyboards (keyboards with a mechanical switch for each key instead of the flimsy rubber dome found in 99.999% of today's keyboards) are becoming more popular by the minute. Once you have used one, you will never go back. There is a passionate community for these keyboards, and some have even gotten together and designed custom keycaps to personalize certain keys on their board. Below are some of my favorites:

• Tsangans Red Alert   ✦  If I wasn't broke, these would be mine, oh yes they would.
• Nyan Cat Number Row   ✦  This is a picture of them on my keyboard. Purchased on a geekhack group buy.
• Beeker   ✦  Beeker has a posse.
• The Riddlers Question Mark   ✦  This is one of those subtle ones that looks REALLY good on a black key keyboard when its the only custom key on the board.