A real American, John Wayne 
I can’t remember what the bills were like, but Irish coins all have the harp on the obverse, and did even before the Euro.
If we put Reagan on the fifty, then can we rename the airport after Grant?
I’m open to any famous person in American history being on our currency. I prefer that anyone considered for US currency be long dead. I don’t want people that are from our recent history to be considered. If there is to be debate about that persons legacy I want it to be in the realm of historians not bar room conversations. So Bush, Clinton, Martin Luther king, Nixon, Einstein all too recent to me. I think a hundred years for names to get out of current politics is a good cool down.
Seriously, you should nuke the politicians and put Quintessential USA Scenes on them instead. One could be all about music, with rock & roll, jazz, ragtime… another might be about transportation, with the Apollo spacecraft, the Model T and the freeways, the DC3, the streamliners… another about building and architecture, with the skyscraper, Hoover Dam, the mall and the strip plaza…
At the very least, the US Mint could just declare open season on the quarter and go wild with it. We could have quarters with famous generals, landmarks, athletes, scenes from movies, animals, food, cars, etc. We could have online polls to vote and every 3 months they’d release some new quarter.
He was trying a little too hard to be the first Black president.
That’s reserved for Barney Frank. 
Rosa Parks
Eleanor Roosevelt
Crispus Attucks
Yet Saudi Arabia and Iran (arguably the most Islamic countries) do.
I think Hunter Thompson would be great on the 50. Have Steadman design it.
I think a bit of compassion from the liberals here is in order.
If you were from the other side and the best you could come up with to honor is someone like Ronald Reagan…wouldn’t you want people taking pity on you?
That’s why I specified “regular-issue” and not commemorative. The Wikipedia article is a bit misleading; the Booker T. Washington half of 1951-54 was also a commemorative. Benjamin Franklin graced the regular-issue half dollars in those years.
John Brown
Christa fucking McAullife? There’s all sorts of crazy in that image. Whoa nelly!
All props to MLK but I like the Frederick Douglass idea better. Tosses some respect to a true badass who is sadly overlooked these days. MLK gets lots of love…let’s spread it around.
Plus, the guy would have the greatest hair EVER featured on American currency.
If it’s gonna be a white dude, James Madison. Father of our Constitution, author of the Bill of Rights . . . without him and his Virginia Plan, we’d have no country, yet he’s gotten very little respect in the way of currency.
I’d like to see a woman or an African American, though. I really like the idea of Frederick Douglass, Eleanor Roosevelt, MLK Jr. . . . and I’ll add Harriet Tubman to the list.
Thelonious Monk. All the money should have pictures of musicians.
Oh, yeah
Ritchie Valens
Janis Joplin
Joey Ramone
Elvis
Would all make outstanding money.
I could agree with this compromise.
And open season on the quarter sounds good to me – we could put on them the Triangle Shirtwaist fire, the Ludlow Massacre, the execution of Sacco and Vanzetti, the internment in concentration camps of Japanese-descended American citizens, and so on and so forth.
Zbigniew Kazimierz Brzezinski?