Best talky movie you ever saw?

[Gladion]

The original Saw might be one, most of the film is just two people in one room talking and figuring out what the hell happened to them.
If you don't let that one count, then I'd say Good Night and Good Luck. Special mention: "Seul contre Tous" (I think it's called "I Stand Alone" in English), that one is just one great, big monologue put over the images - very depressing and partly shocking.

 

[Doc Cannon]

Waking Life definitely. It made me realize I am a determinist.

 

[Srdjan]

12 Angry Men, movie is all dialogue and it perfect.

 

[Henry Michel Proust]

Basically anything from Woody Allen - Annie Hall, Manhattan, Hannah and her sisters, Get the money and run, Bananas, Love and death. Even later ones - Match point, Vicky Christina Barcelona, Interiors.