I love that Spyderco Caly3. It forced my other Spyderco and Benchmade folders almost completely into retirement.

I have a few Leatherman tools and carry the Super (and PocketWrench II and a pile of stuff) in a bag that hangs out inside my laptop bag or in the car, so the weight of anything bigger than a Micra on the keychain probably isn't worth it for me.

I use the Zebra F-301 pen from my keychain without even using the metal half, but I have another one that I use fairly often in the full extended setup gimmick. I did a little work on the rubber o-ring that holds it in place inside the metal half and it stays together better now. Maybe a couple drops of glue or a few wraps of thread under the o-ring would really tighten up the fit. The ink is a little grey, but it writes smoothly and doesn't bleed through a page at all. I've never had it pop open on my keychain. The Sharpie was always falling off until I roughed it up and superglued the cap to the break-away keychain part.

I used to carry a USB key on the keychain, but then I kept winding up with my keychain stuck to my computer back at my desk instead of in my pockets.