"Agrapha" are sayings of Jesus not found in the canonical gospels, but still early enough to possibly be a true saying of Jesus, or a reflection of something he said. The most famous agrapha is the story of Jesus and the woman caught in adultery, with the famous saying being "Him without sin cast the first stone." It doesn't belong in John, where it is usually placed, but it is an important story that gives us insight about Jesus. Here are some other sayings of Jesus that are significant, and gives us insight:
Blessed is the one who has suffered and found life. (Gospel of Thomas)
Let him who has grown rich be king, and let him who possesses power renounce it. (Gospel of Thomas)
For the sake of the hungry, I was hungry.
For the sake of the thirsty, I was thirsty. (Origen, quoting an ancient gospel)
How can you say, 'I have fulfilled the word of God'? It is written, 'Love your neighbor as yourself.' But look, your neighbors are covered with filth and are dying of hunger and exposure, but your house is full of many good things and unused rooms and none of this is given to them. (Gospel of the Hebrews)
He that is near me is near the fire. He that is far from me is far from the kingdom. (Gospel of Thomas)
Hear me, you lambs whom I have chosen, and do not fear the wolves. (Gospel of the Egyptians)