flat wire gate carabiner from Bison designs. (It was originally blue.) Because it's a biner, I can add and remove individual items pretty easily; I can also clip it to the top of my pocket. It's pretty secure, though I still have to make sure everything stays together, lest disaster happen.
Then, starting at the top and going clockwise, I've got:
- My car keys and remote; they're together on their own split ring. Also on that section is an orange Photon II keychain light. For fun, there's a now-obsolete NYC subway token.
- An ARC AAA LED flashlight. It looks a lot like a Maglite Solitaire, but it's not -- it costs 3 times as much (so, about 30 bucks) and it is worth every penny. It's incredibly reliable, practically indestructible, and it doesn't have a bulb to blow out -- the LED will last thousands of hours.
- A Swiss Army Knife Rally, which has a blade, bottle opener, phillips screwdriver, nail file/flat screwdriver, tweezers and toothpick.
- A Spyderco Ladybug knife; it's on a quick-release plunger so I can detach it if I need to go somewhere where knives aren't allowed. It's got a partially-serrated blade that's a smidge under two inches.
- A safety pin. Useful things, those.
- My housekey (The cuts are photoshopped so you can't dupe it from the photo, though if you were going to break in, it would be easier to just make a bump key.)
- A green Traser Glowring -- it will glow in the dark for about 10 years, because it has a little vial of Tritium gas, which is radioactive (but perfectly safe). If you want one in the US, you need to find someone abroad who can send you one, since they're not available here and can't be shipped in.
- A storage capsule, also by Bison Designs; I keep a rolled-up twenty and some Pepcid AC antacid tablets (critically important, for reasons I've mentioned before).
The lights are probably the most useful things. Lights are incredibly handy to have even if you're not worried about blackouts or being stuck in elevators or on the Metro. (Flashlight geeks like to say that there's a 100% chance of darkness every night -- what more reason do you need?)
On any given day, I'll use the ARC for looking under my desk, poking in the dark corners of my laptop bag, or checking inside my mailbox.
The knives I use less often, but only because I usually have a handier knife or multitool available.
Now, there's other stuff that gadget and personal preparedness types might carry that I think is overkill, at least for a primary keychain -- whistles, magnifying lenses, hotspark fire starters, pens, mini-compasses, mini-prybars, small multitools, GI can openers, etc.
Plus, I try to avoid any other keychain junk: USB drives, SecureID tokens, buyers club cards, wifi hotspot detectors, coin purses, condom holders, laser pointers, and the like.
(Besides, if I need to carry any of that other stuff, it'll usually be in another pocket or my laptop bag.)
Short legs = short pants = small pockets, so I don't want too much stuff dangling from my keychain.
As it is right now, it's fairly discreet, with no jingling. Everything goes in my pocket except the car remote, which I let drape over the edge of my pocket.
I guess it also helps that I only need to carry two keys.