Performance(s) that made you sit up and notice an actor

Dan Lauria's performance in Terror in the Family (1996)

http://www.imdb.com/title/tt0117882/?ref_=fn_al_tt_1

Ryan Gosling - The United States of Leland
Ben Foster - Alpha Dog

Yul Brynner in The Ten Commandments (1956).
Elizabeth Taylor and Paul Newman in Cat on a Hot Tin Roof (1958).

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No one could make a greater mistake than he who did nothing because he could do only little.

Most recently, Mark Ruffalo in Just Like Heaven (2005). Just a lovely, easy going, romantic comedy. I've seen him in lots of other stuff, but for some reason this one hit me with with an "Oh, I get it now. That's why people like him so much!". I couldn't even tell you what it was, an everyman kind of thing maybe, I don't know, but it really worked for me.

Jennifer Lawrence in Winter's Bone.

formerly ProfessorAndro

I'm 30, and much of this has to do with the order that I watched their films, not that earlier performances aren't good.

Tom Hardy in Inception, then This Means War and Bronson.

Richard Jenkins in Step Brothers - role of his career?

Samantha Morton in Sweet and Lowdown.

Brad Pitt in Se7en, and then True Romance, etc. The "What's in the box?" scene. Before that I thought he was boring.

Katharine Hepburn - The African Queen.

Paul Dano - There Will Be Blood. The intense preaching scene, when he raises his voice and makes the arm gesture. Haven't been much impressed before or after this.

Daniel Craig, Eva Green, Mads Mikkelsen (everyone but Judi Dench?) - Casino Royale.

Heath Ledger, Julia Stiles, and JGL - 10 Things I Hate About You.

Gerard Butler, Lena Headey, Michael Fassbender, Dominic West, David Wenham (everyone?) - 300.

Rene Zellweger in Jerry Maguire
Lou Diamond Philips in Courage Under Fire
Joan Allen in The Ice Storm
Franka Potente in Lola Rennt
Steve Zahn in Out Of Sight
Alex Kingston in Croupier
Samantha Morton in Sweet and Lowdown
Carrie-Ann Moss in Memento
Naomi Watts in Mulholland Dr.
Ricky Jay in Heist
Chiwetel Ejiofor in Dirty Pretty Things
Andy Lau in Miu Gaan Diy (Infernal Affairs)
Peter Dinklage in The Station Agent
Damian Lewis in Keane
Kristen Bell in Spartan
Joseph Gorden-Levitt in Brick

mf

Trust me. I’m The Doctor.

Thoroughly agree with these suggestions:

Jennifer Lawrence in Winter's Bone (professor_feather)
--- she gets a lot of criticism for her role in American Hustle (2013) but I thought she was the best actor in that, too.

Paul Dano - There Will Be Blood (WeAintFoundShin)
--- I always thought he was rather creepy, but it suited here.
"Haven't been much impressed before or after this." Me neither.

Naomi Watts in Mulholland Dr (MikeF-6)
--- I had seen her around previously but never taken much notice and could not have put a name to the face. This was her breakthrough for sure.

For myself:

A reviewer of Central Station (1998) wrote "Fernanda Montenegro, perhaps Brazil's best actress, is amazing as Dona Dora. She is the whole reason for seeing the movie." I have to agree.

Ann Savage has 43 credits, but her only notable role was in Detour (1945). She was like a wild animal in that and made a low-budget second feature into a Film Noir classic.

Night Falls on Manhattan (1996) contains an electrifying rant by Ron Leibman, an actor I had never heard of. Best scene in this neglected Lumet movie.

Nightcrawler (2014) made me take Jake Gyllenhaal seriously as an actor.

Always thought of Paul Giamatti as a prolific and stalwart supporting actor who pops up a little too often. He is terrific as the lead in American Splendor (2003).

Never liked Thomas Haden Church in anything, but he is hilarious in the rather uneven Killer Joe (2001).