When I rig something up out of spare parts, my wife always points out, "the fact that you end up using all this crap sometime does not mean that you are not a hoarder." That said, the flow of spare items in my household has generally been to cars instead of off of them.
When I was in grad school, I did occasionally use a car antenna as a pointer for seminars.
My best answer to the reverse of your question is using a photoresistor I removed from a VCR in the 1990s to repair the ambient light sensor in my Buick. That little part had been moved a half dozen times–one time across the country–before I finally used it 15 years later.

I'm still using nuts and bolts left over from an MGB head swap I did in 1991.

<img src ="http://i.imgur.com/jXFbI73.gif"&gt;

I'm a frequent abuser of the 'car part as decor' principle. The VW Beetle decklid wall sconce and the Model T rear window photo frame are two of the more recent offenses
<img src="http://i55.photobucket.com/albums/g125/feelmyapathy/20140824_174520_zpsaecf48c2.jpg"&gt;
<img src="http://i55.photobucket.com/albums/g125/feelmyapathy/ModelTFrame1_zpsb6dd98e6.jpg"&gt;