hydration bladder, 2 buttons--1 green 1 black, spare string, superglue, GPS, compass, map, spare socks, spare gloves, magnesium fire block w/flint, pillbox full of tinder, needle and thread(not only for fixing things, but makes a good emergency suture--the superglue will also work nicely for minor cuts), and a couple of sandwiches.
I also have one of those little mini entrenching tools for various chores.
This is a good reminder thread! It seems like everyone carries something different, and we can certainly learn from each other.