I found a sparkling new iPhone 4 on the floor outside the shop last week. Put it in my pocket and walked home wondering what to do with it.
When I got home I turned it on to find it had a lock on it so I couldn't access any numbers on it. The screensaver was a picture of a young girl about 3-4 years old so whoever owned the phone was obviously a young parent.
About an hour later the phone rang so I answered it and told the girl who had phoned where I lived etc to come and collect it, which she did.
She was obviously very grateful and thanked me profusely. At tea time that same night she turned up again with a nice bouquet of flowers and a bottle of wine

Made me feel great knowing that I'd scored some good karma points for me to cash in at a later date.