Jesus Seminar believes that Parable of the Empty Jar in Gospel of Thomas is authentic saying of Jesus:
The kingdom of the father is like a certain woman who was carrying a jar full of meal. While she was walking on the road, still some distance from home, the handle of the jar broke and the meal emptied out behind her on the road. She did not realize it; she had noticed no accident. When she reached her house, she set the jar down and found it empty. - Gospel of Thomas 97
Now, I am not an expert (and I am aware of many flaws of Jesus Seminar), but I think arguments for authenticity of this parable are good.
However, what I want to ask is: Is there any other saying or parable of Jesus that is not recorded in the New Testament, but is remembered in the tradition? Do some Church Fathers quote some words not found in the New Testament, but attribute them to Jesus?