The first time I saw (Actor) was in the movie. ___________

A few that spring to mind :

Tom Hanks - Bachelor Party
Joaquin Phoenix - Spacecamp
Julie Walters - Car Trouble
Kim Cattrall - Porky's
Jack Lemmon - Irma La Douce
Julie Christie - The Demon Seed
William Holden - The Christmas tree
Omar Sharif - The Burglars
Peter O'Toole - Murphy's war
Donald Sutherland - Catholic boys
Kevin Bacon - Friday the 13th
Audrey Hepburn - Sabrina
Kirk Douglas - Spartacus
Michael Caine - The Italian job
Grace Kelly - To catch a spy
Sophia Loren - Houseboat
Fred Astaire - The purple taxi
Tom Courtenay - The loneliness of the long distance runner
Gregory Peck - The Omen