People that changed history

Many people has changed the course of history, some through science, art, medicine, and so on. One of my favorite is Beethoven, I can say that he change music from its basis, he change the way to compose and perform music. After him everything was different, I guess that without him modern music would not exist.
Who is your favorite character from history? Why?

Fictional heroes

There's a universe full of great heroes and nice characters that make us dream and laugh, some of them come from comics, books, movies, cartoons and even legends. One of my favorite characters is Sherlock Holmes, he is a genial, intelligent, extravagant and brave all at the same time, no matters how difficult is a crime, he will discover everything about it.
Well, What about your favorite character?