Some of my favorites are the classics:
Already mentioned:
Eye of the Beholder
Monsters are Due on Maple Street
Nick of Time
Time Enough at Last
The Invaders
Some others:
The Howling Man: A man has the devil locked up, but can he keep him. Excellent photography (camera tilts when the main character goes delirious).
Printer’s Devil (an hourlong episode). Burgess Meredith plays a man who saves a struggling newspaper; for a price.
Five Characters in Search of an Exit: A soldier, a clown, a ballarina, and two other characters (whom I can’t remember offhand) find themselves in a room with no exit and no memory of who they are and how they got there.
Rip Van Winkle Caper: Some crooks decide to pull off a gold heist and have themselves suspended for 100 years, thus leaving the trail cold. The fun starts when they wake up.
A Game of Pool: Jack Klugman and Johnathan Winters have a supernatural billiards game. Be careful what you wish for, you just may get it.
Will the Real Martian Please Stand Up?: One of the characters is an alien in disguise, but which?
Nightmare at 20,000 feet: A classic. I’m surprised no one mentioned this one
One for the Angels and Escape Clause: In both episodes, a man makes a deal (one with the angel of death, the other with the devil). In both cases, of course, the deal doesn’t turn out as they planned.
Anyway, those were my favorites:
Of course, my mentioning the episode of 20,000 feet made me think of a recent episode of 3rd Rock from the Sun.
William Shatner (playing the Big Giant Head) gets an airplane. The aliens (John Lithgow and Co.) are waiting for him. Lithgow’s character asks him how the flight was.
“Horrible,” says the Head. "There was this little creature on the wing (a reference to his 20,000 feet episode).
“I know!!” says Lithgow. “The same thing happened to me!” (Lithgow played the same character in the Twilight Zone movie).
Zev Steinhardt