There are actors/actresses who have and will star in great films and give brilliant portrayals - but will always be remembered for that one defining role (Oscar optional).

Anthony Hopkins in Silence of the Lambs 1991.
as Hannibal Lector.
This can go on to include the films Hannibal and Red Dragon, but Silence was the one that started him off in this vein. He even won an Oscar for Best Actor for his role.

We all know Sir Anthony Hopkins has been in the business for many, many years, and has starred in such great films as The Elephant Man in 1980, but he will forever be remembered as the chilling Doctor Lector.

Sylvester Stallone in Rocky 1976.
as Rocky Balboa
Rocky...uh, Sylvester has gone on to play Rambo which had numerous sequels, but you see Sly on the screen, you wanna yell out Yo, Adrien!

Sly Stallone gets Oscar's attention with his career defining role with nominations for Best Actor and Best Original Screenplay, and the film went on to win Best Picture of 1976.

A few I can think of...

Schwarzenegger - The Terminator
Eastwood - Dirty Harry
Bela Lugosi - Dracula

Dustin Hoffman - The Graduate

Now, me - when I think Dustin Hoffman, I think Rain Man.

For me, too, Dustin is Rain Man.

Another one, I don't care how much success he's had recently, Dennis Haysbert will ALWAYS be Pedro Cerrano to me.

Peter O'Toole - T.E. Lawrence
Ben Kingsley - Mahatma Gandhi

Marlon Brando as The Godfather

Wow. I almost mentioned Brando...

...for On the Waterfront.

Tom Hanks - Forrest Gump
Harrison Ford - Indiana Jones
Bruce Willis - John McClane
Al Pacino - Michael Corleone
Robert De Niro - Sam "Ace" Rothstein

Orson Welles - Charles Foster Kane
Peter Sellers - Inspector Clouseau
Clint Eastwood - Man With No Name
William Powell - Nick Charles
Anthony Perkins - Norman Bates

Two words:

Travis


Bickle

Though he played many a great role over the years, George C. Scott will always be remembered for his portrayal of General George Patton.

In addition to Indiana Jones, Harrison Ford will forever be known as Han Solo.

Same w/ Peter Sellers as Dr. Strangelove.

Paul Newman - Cool Hand Luke (or for his role in the Hustler, etc., etc., etc.)

Jeremy Irons - Claus von Bulow
Jack Black - Barry (High Fidelity)
Michael Douglas - Gordon Gekko
R. Lee Ermy - Sgt. Hartman
Dudley Moore - Arthur Bach
Malcolm McDowell - Alex
Carrot Top - Edison

John Vernon: Dean Wormer

Redcon1

Tom Cruise - Pete Mitchell
Cuba Gooding, Jr. - Rod Tidwell
Jim Carrey - Ace Ventura
John Travolta - Johnny Barberino/Vincent Vega (depending on your age)
Keanu Reeves - Jack Traven

And I can't believe no one has mentioned:

Christopher Reeve - Superman/Clark Kent/Kal El

James Stewart as George Bailey
"Mary! Marrryyyy!!"

Dennis Hopper as Howard Payne

Chevy Chase - Clark Griswold
Michael J. Fox has the distinction of having a defining role in both Film and TV: Marty McFly and Alex P. Keaton

Ralph Macchio - Daniel LaRusso
Christopher Lee - Dracula (?)
Val Kilmer - Doc Holliday and/or Chris Knight

Mr. Anderson. . .

Hugo Weaving - Agent Smith

Harold Ramis - Egon Spengler

Kevin Smith & Jason Mewes - Jay and Silent Bob
Michael J. Fox - Marty McFly
Christopher Lloyd - Doc Brown (But don't forget his character Jim from "Taxi", even if it was TV)
Bruce Campbell - Ashley J. "Ash" Williams
Sigourney Weaver - Ellen Ripley
Michael Keaton - Batman/Bruce Wayne
Charleton Heston - Judah Ben-Hur
Gregory Peck - Atticus Finch
Mel Gibson - William Wallace/Martin Riggs


And this is pure spectulation:
Tobey Maguire - Spider-Man
Jake Gyllenhall - Donnie Darko

Vinnie Barberino maybe?

I would have thought of his role as "Neo" in the Matrix trilogy before his role in Speed.

...and Kal, Val Kilmer will forever be remembered as "Iceman" in Top Gun, w/ "Doc Holliday" coming in a distant second.

And John Wayne will forever be remembered for playing John Wayne in every last one of his wonderful films. Except when he played "Sean Thornton" in the Quiet Man, of course.