~Books.
~Good music that makes my blood go wonky.
~Laughing.
~Being with my friends! Just doing stuff. Or even sitting in silence. Just being, y'know?
~This is a silly one, but it's such a great feeling to wake up on a school morning BEFORE your alarm goes, looking at the clock and realising: "Hey! I got two more hours of sleep!" -- it's so satisfying.
~Doing stuff; always having a purpose, a porpoise and/or something to be busy and tired about!
~Good food...?

I'm sure there's more, but these spring immediately to mind. Ditto what BoB said, too.