Martin Luther changed history in a religious way. He started off as a poor man, and then later in his life became a small time priest. As he became a monk, he saw that the pope and the church were misleading the people in order to make a bit of money. He went against the church and did everything in his power to set people back on the right path. Even though he was excommunicated, he still held on, and that is how Martin Luther has a great impact on the course of history.
Bill Gates, as many of you may already know is a very rich man, if not the richest man in the world. But this was not the case when he was a young man. In fact he was very poor and he dropped out of school at a young age. A couple of years later he created Microsoft, the largest computer company in the world. Today he has over forty billion dollars and donates billions of dollars to charity. Although some people don't agree that he has changed history and still is, I think otherwise. I mean take a look at the number of computers in the world; you will see that most of them are powered by Microsoft.
Adolf Hitler, in my opinion has changed the course of history in a bad way that any other person in the world. Although he wasn't rich at a young age, he became rich and very popular in his later life. He developed a strong hatred for the Jews which led to him killing thousands of them. This was known as the holocaust. Although many people don't know what happened to Hitler after these events, many speculate that he poisoned himself.
Over role these three historical icons have changed history in a significant way. Just to answer your question about average people having a significant impact