Ditto…
The same is true of cigarettes, now that I think about it.
On me, I have a little flashlight and a bottle opener on my keyring. And in my change purse, I carry a pocket knife and, in case of first aid emergencies, a pair of surgical gloves and a CPR one-way barrier.
Never had to use the first aid gear yet (thankfully), but I use the rest of the stuff all the time.
Dental floss.
Have you ever had an apple or barbecued ribs or corn on the cob at lunch and then been driven insane all afternoon because you were unable to remove fibers from between your teeth?
Dental floss.
Cell phone
Wallet w/ ATM cards
Keys
Small pocket knife
Handkerchief
Lighter
Bag of tobacco
Rolling papers
- When commuting:
Folding bike
Backpack containing:
Macbook
One or more paperbacks
Pen
Some paper
Bottle of water
USB thumb drive
Tooth brush
Woolly cap
Pair of clean socks
edit: and sunglasses! useful even in wintertimes when the sun is low and shining in your eyes
I always carry a pen and notepad to write down ideas as they occur to me. I also have a pocket-sized video camera that actually films a rather high quality picture in HD, considering it’s size (it’s called the RCA Small Wonder). Never know when something’s gonna bust out that I want to film.
Other than that just the standard stuff: wallet, keys, cell phone, and (sometimes) mp3 player. That stuff is enough to fill up my pockets already, and I usually wear cargo pants, fer chrissake. I’d like to carry other stuff, like a utility knife or PDA, but I don’t have room, and I’m not about to buy a purse. 
I don’t want to hear the story about the Constitution. I want to hear the one about the eyepatch. ARRGH! 
As an associate at Wally world, I carry these in my pockets while on the clock (note: I’m right handed): in left pocket, chapstick, a pen, a quarter (the first day I worked, a teen asked to bum a quarter in the bathroom. I’ve kept at least one quarter ever since). In my right pocket, a baggie w/some trail mix (it keeps me from dragging).
Love, Phil
Roofies and condoms… (just kidding. Although to be honest condoms do come in useful sometimes and not always for you know what)
But seriously, rubber bands, a swiss army knife, my ipod (coz it doubles as a 30gb portable hardisk) a lighter and a pdf reader on my phone to read my favourite e-books. Ooh, and spare change. Always useful.
Mini spools of white and black thread along with a couple of needles.
Slight hijack, but how come you can’t get all of the Swiss Army Knife doodads separately, so you could make your own custom knife? I mean, ever look at the huge knives they sell? Always lots of stuff you don’t need, but then again the smaller knives are always missing something that looks handy.
Victorinox, I beseech you! Heed my call!
They have several models. Choose the one that has the doodads you want.
Because if you made one yourself you know you’d end up with this.
(ohh… well I might need this… and if this happened I might need that… and that would be pretty cool…)