One minute writer: What's the most useful tool you own?
Most people don't think of their computer as a tool, but it is. Mine helps me to keep track of my finances, write letters, contact friends, play games, plan TV watching, read books, practically everything. I couldn't live without it. It's certainly the most useful tool in my box. (Though you can't undo screws with them!)
Written for One Minute Writer. See link on the left.