If you've found yourself asking that question more than once in the past few months, or if you spend a lot of time lurking in dark alleys, you might find this tiny Zipper Watch Light useful. It attaches with climbing rope clips to anything, and displays the month, day, hour and minute as well as lighting your way. It's $9.95.

Zipper Pull Watch & Light [Flax Art & Design, via Red Ferret Journal]