Carole Ann Ford
Day of the Triffids (1963)
* Now obviously I love Carole as much as the next person, but I don't mind saying that I'd never considered her the world's greatest actor. So take heart that she's really good in this, as a blind girl—which won't shock anyone familiar with the source material, and isn't a spoiler to those who aren't. The film itself isn't great, and I wonder if something went wrong in the digitisation, because the colour can be physically difficult to look at at times. If not for Carole I'd recommend just reading the book. You should probably read the book anyway.
William Russell
Above Us the Waves (1954)
* Very good war film. Nothing else to add really, but Russell makes a more than decent fist of his character's Scottish accent.
The Adventures of Sir Lancelot (1956-57)
* Rejoice: this series is on YouTube. (In fact so is the film above I believe.) It's quite fun.
Superman (1978)
* To be completely honest it's a bit sneaky putting this on here. I've seen it loads of times and never spotted him—but turns out he is there, and it's worth mentioning anyway just because it's the best superhero film ever made.
Blackadder (1983 episode)
Jacqueline Hill
The Blue Parrot (1953)
Maureen O'Brien
Casualty (1987, bits)
Victorian Scandals (1976 episode)
Peter Purves
Blue Peter (bits)
* I wouldn't normally include this either, but it gives me an excuse to share this delightful clip.
Jean Marsh
The Ghost Hunter (various episodes, 2000)
The Twilight Zone (1959 episode)
* Aside from Doctor Who (natch), this is my all-time favourite TV show. It's classic Doctor Who (black-and-white, slow-moving) in a modern Doctor Who format (standalone, half-hour episodes), and if it isn't terribly consistent, it does have a mighty selection of sensational, A+ episodes. Jean's is one of the middling ones: "The Lonely".