Oh, goodness me. I'm not even going to start a list of the junk that's kept in the garage (I don't have one, but dad has two, and a cellar).
I do have loads of bits for a Mini. Which were very useful once upon a time, but I got rid of the Mini about 10 years ago... See post in the for sale bit
I took about 5 car loads of stuff to the tip earlier in the year, that made quite a good start on some of the *ahem* valuable possibly useful artefacts that had been stored (aka junk).
We also have a collection of 'useful' metal. Though I think it may actually now be down to just the useful parts, as we had a blitz on it about the same time I was taking stuff to the tip, and got rid of the metal that was more rust than anything else and/or so bent that it wasn't going to be of any use at all

I did have to counter various "but I've been keeping that for 30 years!" arguments before I managed to get rid of various things, mind you...
