My most used 'tool' to design code is a bottle of coke and a cigarette. When i need to really think of how to do someting i leave the computer for a while, when i come back after a break I've solved the problem, most times.

I use paper in landscape mode or portrait mode when i really have to draw something. I usually draw only rough pseudocode, or just boxes which represents functions, objects or DB tables, pending on the problem.

/wonko