You could make a compelling argument for a whole lot of Bresson films, even though he only made 14 of them (and nine of them received votes in the last Sight And Sound poll). I'd choose only one of Pickpocket or A Man Escaped, because they are relatively similar. And I can't imagine watching three Bresson films and not having one of them be Au Hasard Balthazar or Diary Of A Country Priest. Those films, and the religious/transcendental interpretations of them, are so central to Bresson's reputation as a director (FYI: Paul Schrader doesn't know what the hell he's talking about). Balthazar's the better film, and it's the kind of film most people wouldn't watch outside of a marathon-type environment (a biopic of a donkey?? WTF?)
I just watched The Trial Of Joan Of Arc a couple days ago, and I liked it a lot. Lancelot Du Lac is coming from netflix today and I'm really looking forward to watching it.
Anyway, my suggestion:
Pickpocket
Au Hasard Balthazar
Mouchette
The Sound And Sound votes:
A Man Escaped 2 Critics, 2 Directors (Olivier Assayas and Errol Morris)
Au Hasard Balthazar 10 Critics (incl. Manohla Dargis, Donald Richie, Gavin Smith, Any Taubin and Adrian Martin), 2 Directors (Michael Haneke and Aki Kaurismaki)
Diary Of A Country Priest 1 Critic
Four Nights Of A Dreamer 1 Director
L'Argent 3 Critics (incl. Kent Jones), 2 Directors (incl. Olivier Assayas)
Lancelot Du Lac 2 Directors (Michael Haneke and Catherine Breillat)
Les Dames Du Bois De Boulogne 2 Critics
Mouchette 1 Director (Jim Jarmusch)
Pickpocket 2 Critics, 5 Directors (incl. Paul Schrader, Richard Linklater, and Theo Angelopoulos)
So this has Balthazar, Pickpocket and L'Argent as the most acclaimed. Though one Jarmusch is worth at least three Hanekes.