Hard to beat a Victorinox Swisscard:
LED mini white light; 13 tools include: Letter opener/blade, scissors, rulers, tweezers, magnifying glass, straight pin, pressurized ball point pen and Phillips screwdrivers
I'm inclined to trust this recommendation based on your username alone. But yeah, that looks insanely cool, and now I want one. :)
Yep, I want one too now.
Keys. I must have my keys. Having been locked out of the house twice and two different cars, I have them on me at all times.
A little notepad and pen or pencil.
You can take notes on your phone, but you can never leave someone a note on your phone! I mean, unless you want to duct tape your phone to their door saying, "I dropped by, be back again later," or something. It's your call dude. No one's telling you what to do.