Randy Pausch.

If you haven't heard about Randy Pausch or watched any of his on-line lectures (I am watching this), I strongly recommend that you do it now.

He is a truly inspiring person, and extremely funny too.

I am generally a happy bunny and glass-is-always-half-full type of person, but I would kill to be half as optimistic as Randy is. He is amazing.

Some quotes:

"Experience is what you get when you didn't get what you wanted."

"..when you are pissed off at somebody... you just haven't given them enough time. Just give them a little more time and they will almost always impress you."

"The brick walls are there for a reason. The brick walls are not there to keep us out. The brick walls are there to give us a chance to show how badly we want something... the brick walls are there to stop the people who don’t want it badly enough. They are there to stop the other people."