My keychain has:
a Leatherman Micra
a Solitaire with a Tektite LT-3 drop in LED
an aluminum whistle from the toy store
a Metal Match
no keys
That's right, no keys: they're in my wallet. Drivers license and car key belong together. Work key in my briefcase.
The Solitaire with the LED is a practical light. There's a definite yellow-green cast to the beam, but it's bright enough to see by. The only real negative is that Tektite says that you shouldn't use the lithium AAA's because their 1.7V output voids the warrenty. I already had the Solitaire, so I looked for an adapter. If I had to do it again, I'd probably buy an Arc or a Peak Matterhorn.
The aluminum whistle is one I got for stocking stuffers for the kids. They lost interest (good thing, too: they're loud!), so I took one and use it to call them when we're outside.
The metal match is from countycomm, and a new addition. We'll see how useful and practical it is, and whether it holds up to life in a pocket.