A while back I'd mentioned the cruise control on my truck was acting up; Og suggested cleaning the connector and putting some dielectric grease on to keep it clean. Made a world of difference.
So, about two months ago I was having trouble with the MP3 player I'd picked up; the sound would sometimes break up if the earbud plug wasn't just right. Idea struck: cleaned the plug, wiped a thin coat of the grease on, worked it in & out a few times, then wiped the plug off; haven't had a problem since.
One more: I've got a couple of those inexpensive LED flashlights that use three AAA batteries in a cage, and every so often the damn things will start cutting out if you tilt them. Cleaning the contacts helped, but didn't last. So I opened them up, put a dab of the grease on the top & bottom contacts of the cage, and so far no more problems.
That little tube of grease is going a long ways.