I have this ongoing pet fear:

My cell phone falls out of my hands and falls through the grating in the street into the sewers. It's so small and slim and slippery, I worry it will happen. Then, of course, all the people stare and laugh at the annoying cell-phone user (me) who lost his precious cell-phone.

Not an important fear in relation to so many other issues, but a small one that's consistent.