Here's a guilt complex for you...

I lived in a ritzy yet cozy little city in California, one too expensive for me to own a car, but it had a very good bus system. Walking home from shopping and eating out one night, I found three $100 bills lying in the grass. They looked and felt like they had been there for a long while, but because of the grass few if any people would've spotted 'em if they weren't looking for them.

It was late, I was on one of the busier streets (the busiest in the county during rush hour), and there was very little car traffic and absolutely no foot traffic for as far as I could see. I didn't realize what they were until I was already holding them in my hands.

My only choices were to either keep the bills and be on the lookout for their former owners, or to put them back where someone without as clear a conscience could spot them much more easily than I did. I kept the money, and I never saw or heard from anyone who might have lost some money. I tried for a week, before giving up and keeping the money to spend.