Abraham Lincoln was the 16th president, and is considered one of the best by historians. He's considered great for guiding the country through the Civil War. He was also the first president to be assasinated in office, started his Gettysburg Address off with "Four score and seven years ago...," and was the tallest president, who looked even taller with his hat on.
He has appeared in almost 2 dozen animutations. His most major role was in Hyper Lincoln! Additionally, he did something NSFW with Karl Marx. Most of the time when he appears, it tends to be on Mount Rushmore, or a penny.