These are not in order, they're too different from each other to rank.
Top 5 Speeches
Nr. 1: Inglourious basterdsThe Nazikillin' speech - "We're gonna be doing one thing, and one thing only. Killin' Nazis"
Nobody writes dialogue like Tarantino but I can't put my finger on what makes it so entertaining. Very strong performance by Brad Pitt as well.
Found a cool video of the speech on youtube:
Nr. 2: The Grapes of WrathThe Liberty speech - "Where ever there's a cop beatin' up a guy. I'll be there"
A very powerful speech well acted by Henry Fonda, my favorite actor of older movies.
Everybody should listen to the song "The Ghost of Tom Joad" by Bruce Springstein and the cover by Rage Against the Machine.
Nr. 3: The HangoverThe Wolfpack speech - "I've just added two more guys to my wolfpack"
I don't know who wrote this speech, but I have to say much of the credit has to go to Zach Galifianakis for his acting. It's really thanks to him the movie was good, otherwise, it would've been decent. He couldn't save the sequel though in my opinion.
Nr. 4: FestenThe Unveiling Speech - "I realised that Helge was a very clean man, with all those baths"
This is perfect, if you haven't seen it, do now! The cold way Christian holds the speech, acting like there is nothing special about the speech and not giving away anything before the disclosure.
I suggest you watch the movie before watching this videoclip
Nr. 5: The Great DictatorThe Humanity Speech - "You are not machines, you are not cattle, you are men!"
A great attack on the Nazis by Chaplin.