Most of the time they are disappointed with my answer when I tell them that there is no special tool. You just have a pick a tool you like and apply your methods, your knowledge your skill and repeat until you get it right.
If you are interested in this topic, I have three book suggestions. A Whole New Mind by Daniel Pink. The Rise Of The Creative Class by Richard Florida and Linch Pin by Seth Godin.
I am pretty sure you are not going to ask me what tool I used to create the Cartoon strip above. :)