My favourite would have to be the Rainbow Fish. Not sure how well known it is though, so I'd best give storytelling a go ~
There was a poor man and his wife that lived in a little rundown hut in the forest. One day, the man went out fishing when he caught a fish. The fish was beautiful, with scales that glittered and were all the colours of the rainbow and more. To his great surprise, the fish then spoke and pleaded for the man to let it go.
"I'm a magic fish!" the fish says, "Please, if you set me free I can grant you a wish, any wish you like."
The man considers this. The fish did indeed seem magic, with it's wonderful scales and ability to talk.
"Okay," says the man, "I wish I had a beautiful house, that doesn't leak in the rain, or fall apart in the storm. I want it to be big and special."
With that, he threw the fish back into the lake and went home.
Upon his return, he found his hut was no longer there. Instead there was a beautiful stone building, with ivy creeping up the sides. His wife ran outside to him, screaming with glee.
"It's so beautiful," she cried, "how did this happen?"
The man explained all about the Rainbow-coloured fish and the agreement he'd made.
"You're an idiot!" The woman screamed, "Why did you let it go? We could have been rich! Go and catch it again and bring it back here!"
So the man went back to the lake, and began fishing again. It wasn't long before the Rainbow Fish was hanging off his line again.
"Fish!," said the man, "I am taking you home."
"No please," said the fish, "If you let me go, I will grant you another wish. But you must also promise never to seek me out again, or I won't grant it."
The man considered and agreed. "I wish to be the richest man in the land, with money to spare and jewels to make even the king envious." And with that he tossed the fish back into the lake.
Upon returning home he found his home full of gold and gems. His wife, buried deep in a pile of coins, shouted with joy.
"You did it! You returned with the fish and now we are rich!"
The man explained that he had let the fish go again, so that it would grant the wish. At this the wife became angry, and told him he was stupid. If the fish could grant wishes, it could grant them, whether they threw it back or not. It was being stubborn. "I want that fish," she screamed, "You stupid man, get me that fish!"
The man asked her why? What more did they want. They had a beautiful home and they were rich. The wife screamed and threw a golden glass at him. He fled the house and went to the lake.
After a little while he found the rainbow fish on his line once more.
"Oh fish," he said, "My wife is horrid. She wants more and more. She wants me to take you back and make more wishes."
"I won't grant them," said the fish, "You said you would not seek me out again. And you have"
"I won't throw you back," said the man, "Unless you grant me another wish. I wish that my wife was young and beautiful and kind."
He threw the fish back.
Upon hitting the water, the fish became dull and grey, like all the other fish. It turned and looked up at the man.
"Now you will not know me. I am a fish, like all the other fish. If only the gifts of strangers can make you glad, and greed your only goal, then you will never find happiness." And with that the fish disappeared back into the lake.
Upon returning home, the man found his old hut waiting for him. No stone home. Inside there was no gold or trinkets. Only his wife, who was now the ugliest woman he'd ever seen.
Lessons behind it? Greed is bad. The magic fish became normal at the end, so that it would blend in with the other fish - sometimes advertising certain talents isn't a good idea. Or maybe that women are evil
