The Good Samaritan
I made the mistake of leaving my credit card behind, inside one of those self-serve machines, at Kinko's. As soon as I realized what I had done, I rushed back to the store in a panic.
It turns out that some random stranger had found my credit card and turned it in to the store's management. A quick check with my bank confirmed that there were no unauthorized charges to my account.
To the unknown person who did me this great favor, I simply say "thank you!"