I hate throwing anything out that I feel might be of any use at all to anyone else, even down to paperclips, and I hate throwing anything out that I think I'll want to look at in the future (souvenirs, etc). Which is why I'm currently having such trouble sorting out my cellar, jam-packed full of everything that hasn't got a home upstairs.
The urge to save things has come in handy on occasions though. The DGS all enjoy playing with the Lego, Sylvanian Families, jigsaws etc that I couldn't bear to throw out when my lot outgrew them. And DS, the captain of the "Get rid of it all, Mum" movement of 20 years ago, has just identified a rare Star Wars character that's worth over £200. He's taking a keen interest in my boxes now (though maybe not the 5 containing the mainly homemade fancy dress outfits....).