I'm pretty much a minimalist when it comes to these things. And since I live in L.A - I don't carry things like a fire starter, tinder, foil etc. Nothing special - but here is my list:

1. sports watch
2. Nokia cell phone
3. small mp3 player
4. 36 oz. water bottle (I make it a habit to constantly drink water - good for the kidneys)
5. pocket note book and compact pen
6. thin wallet w/ I.D cards, bank cards, phone card
7. small "man purse" with change and $10-$20 cash
8. carabiner w/keys, 2 photon lights, cheap little aluminum whistle from REI, and a thermometer/compass (don't really need it - but I just like knowing the temperature)
9. mini L.E.D flashlight
10. small plastic case w/ tweezers and 2 sewing needles (I seem to have really bad luck with splinters)
11. Leatherman Micra
12. Spyderco Rescue 93mm or Spyderco Assist (I really like the light weight and full serrations because I suck at sharpening; also, these knives are not "malicious" looking - so people don't freak out when I happen to take it out to open a package or cut a sandwich)