I’m surprised that no one has yet mentioned the brilliant performance by mentally ill street musician Bruno S. in Werner Herzog’s masterpiece The Enigma of Kaspar Hauser . It’s the ultimate acting performance by a non-actor, and everyone should see it.
There was Tom Braidwood, who played Frohike (one of the Lone Gunmen) on The X-Files.
As the story goes, he had been an assistant producer on the show since the beginning. And when they were tossing around ideas for the role of Frohike, they kept using Braidwood as an example of the different characteristics that they thought Frohike should have. Eventually, they just went ahead and offered him the role. And he was perfect in it.
No idea if anyone’s mentioned it - considering the board, someone probably has - but Maria Falconetti in the 1927 The Passion of Joan of Arc is brilliant. Hell, I loved it even as a High School student with a disdain for “classic” black and white movies.
Zombie thread, but I will mention David Bowie.
MrDibble in Night of the Zombie Threads. 
A friend of mine works for director Henry Jaglom, who often does “atraditional” casting. The way she explained it, a character in one of his movies (“New Year’s Day,” 1989) was having trouble connecting with one of the actors… maybe it was during the casting process, I’m not sure. Anyhow, the character said her boyfriend, who was a grad student–an English major–was more like the way the character was written in the script. So Jaglom called him in, ended up giving him the part.
It was David Duchovny.
So you could say Duchovny was a non-actor. 
I would add Wolfgang Bodison Who played Lance Cpl. Harold W. Dawson in a Few Good Men. His only previous IMDB credit was as an assistant to Rob Reiner on Misery.
He nailed that role.
In all fairness, her delivery was supposed to be totally flat. My uncle thought she was absolutely hilarious and would cackle like a demented rooster every time she said something in that bland, wooden tone.
Dr. Fleishman (paraphrased): “He’s going to launch a cow with a catapult! That’s barbaric!”
Marylin: “We’re going to eat it afterwards.”
Back to the OP, I don’t know if this was mentioned, but wan’t the guy who played Xander on Buffy originally a production assistant? (Not on that show though). Not that his performances were Emmy-worthy or anything.
Wait, this is a zombie thread? :smack:
Ditto Jaime Presley, the model-turned-actress who richly deserved the Emmy she won for My Name Is Earl.
The guy who played the demonic Bob in Twin Peaks was a production assistant who, the story goes, struck David Lynch by how scary he looked as he was setting up the lights.
Although I don’t care for his music, I’ve been impressed by how well Justin Timberlake does in every small acting role he’s had. I’ve read that he so impressed the SNL producers that they give him more sketches every time he’s on.
Re: singer-songwriter-actor Hoagy Carmichael, Ian Fleming once said that he envisioned James Bond as looking like him.
Jeff Healey as a musician in Road House. Not that it’s saying much, but he was much more convincing than Patrick Swayze.
Interestingly, Airplane was not Kareem Abdul Jabbar’s first movie - he had done some small TV work before, and he is in the unspeakably creepy Game of Death , a posthumous film stitched together after Bruce Lee’s death, and whose plot foreshadows the tragic death of Brandon Lee on the set of The Crow
Alex Karras was very good as George Zaharias, husband of Mildred ‘Babe’ Didrikson, in the Golden Globe winning 1975 TV movie.
Edit to add - sorry, I didn’t realize this was a zombie thread, it popped up in New Posts.
Jocelyn LaGarde in “Hawaii”
The first time she walked on screen I thought, “Well, here’s the model-turned-actress. Every series has one.” About halfway through the second hour I was thinking, “Jesus, she’s good.” She’s creepy and frightening every minute she’s on screen.
:smack:
That’s the problem with having the search results tab open next to the thread listing tab. 'twas Henry Rollins that dragged me in here.
Fred Thompson was not an actor before playing himself in the movie Marie, which featured Sissy Spacek.
Everyone in Pasolini’s Gospel According To St Matthew. A great film in every respect, and definitely the best telling of any version of the Gospel. Not a single professional actor anywhere near it. To my mind, this is not a coincidence.
Maybe he’s been mentioned already, but there’s also N!xau, the star of The Gods Must be Crazy. And I believe the two male leads of Goin’ Down the Road, the greatest Canadian film ever, were non-actors.
Director Sidney Pollack does a good job when he occasionally steps in front of the camera.
Hey, has anybody noticed this is a zombie thread?
Before he played himself in Sunset Boulevard, Cecil B. DeMille had done some narration and extra work, but had never really been an on-camera actor. I thought his performance was pretty good, but then the movie is awesome in every respect, so his was one of many.
Robin
You misspelled Casino.