I stumbled upon some old btc wallet backups from a very long time ago. I had emptied most of them but several had small amounts of 'dust' still sitting in them (.004btc, .006btc, etc. even some .01's!). At the time the price was low enough that I really didn't care about losing a little dust on a given transaction but, fast forward to today and my collective pile of dust is worth over $10k!

Thank god I never deleted those backups!

PSA: If you were using bitcoin in the early 2010's and still have wallet backups, sweep out the dust!