Well, personally I found the following:
>> a wad of $10 & $50 bills dropped from someone walking
in front of me on an overhead bridge when I was in Primary school -
I picked up the wad of cash, ran up to the man and gave it all back
to him... and later felt I could have done otherwise... 
well.. I was
young...
>> Found a wallet containing money and ID cards along with
other personal effects in the toilet of a shopping center; I
submitted the wallet to the information counter, and demanded that
they get the owner to contact me when he collects it to make sure
it was returned.
>> got into a cab after a rather rude Mandarin speaking lady
alighted and slammed the door on me, and discovered she left behind
her purse containing keys and over $200; I kept the money and threw
away the keys... she dserved it and there were no indentity card
inside.
>> found an entire clutch bag near a traffic junction while
driving; it belonged to a Malay dispatch rider, whom I personally
drove to his residence in Teban Gardens and handed it over to his
wife. There was not much in terms of money in the bag, but it
contained the man's Quran book. That in my opinion, is VERY
important.
Over the decades, have picked up various denominations in money
that people dropped, but no way to trace ownership. So pocket them
lah... 
hmm.. come to think of it, someone even paid for my petrol at one
Shell station and drove off, and the cashier said she paid for me!
I was so stumped..!
