1. A Large Mallet
2. A flat head screwdriver, or perhaps even a chisel
First, take the screwdriver and plant it firmly in the crevice under the key to be removed. Then, using the mallet strike the keyboard hard enough to pop the key into the air without cutting all the way throught the keyboard. Pick up the key, and modify it in whatever way you want. Some good ideas are carving it, painting it, glueing other items to it, or just crushing it into dust. After the modification you can re-attach it to the computer in whatever way you desire, we recommend hitting it back onto the keyboard with the afore-mentioned mallet.
Click on the image for a demonstration in Quicktime (3.9 meg).