The 20th century is a very interesting anime that all should enjoy. It involves spicy characters with a touch of great plot. For example, the main character, Hitler, is an over-powered, psychotic, typical anime character. What makes him different, however, is his special knack for slaughtering citizens who practice Judaism. A move of his that is cherished by millions is his gas attack, where he forces the Jew into a large, metal chamber, and fills it with Zyklon B, a deadly gas.
Personally, my favorite arc is the Vietnam Arc. In this story arc, we get to see one clan, the Americans. face off against a smaller, but potent clan, the Viet Cong. The Americans are over-powered and use their napalm weaponry to obliterate the poor families of Hanoi, the home base of the Viet Cong. However, the underdog Viet Cong reigns victorious in the end and dishes out the first defeat ever to the Americans.
All in all, I would say that the plot and characters of this anime are enriching, and I would recommend anybody to watch this. They recently made a sequel to the show called The 21st Century. There's this new main villain and he does some crazy, funny stuff. His name is Osama bin Laden, and he comes from the clan of Arabians. I won't delve into too much detail, as I don't want to spoil it for you. If you watch the 69th episode of The 20th Century, you will see a building complex being built by the Americans called the World Trade Center, which made the Americans clan wealthy. Let's just say, our new villain and these towers are some pretty extravagant features in the first story arc.
All in all, crazy, funny, and cool. I would definitely recommend this anime and its sequel.