AAA 12V air compressor

After waiting in line at the gas station to fill my leaking tire last week, I decided to try my 12 volt air compressor this time. It did a great, if noisy, job. Good to know - I keep the compressor in the trailer for emergencies.

It made me think of all the stuff I carry 'just in case'.  Some of it I use all the time - but some of it has never been out of the box!  Would it really work if I need it?

How about you?  Have you actually used everything you carry?