The Monsters are Due on Maple Street. If only because we had to read the story in elementary school a long time before I ever sat down to watch The Twilight Zone. Imagine my surprise
"The Shelter" -- The scariest episode in my opinion by far.
"Time Enough at Last" -- The most classic of course
"The Self-Improvement of Salvadore Ross" -- always sticks in my mind, and truly great premise.
"What you need" -- This episode is extremely satisfying to me.
I bought them a while back (on DVD and on iTunes/AppleTV) and go through them from time to time. Syfy can't figure their shit out anymore. They used to bring us amazing stuff like Battlestar Galactica. Now... just a shitshow like all of the Cable networks.
When I was younger we’d get a couple cases of beer and try to watch the whole marathon without sleeping. Try to do the same with the classic Star Trek marathons as well.
"The Other Place" - I try to watch it anytime I see episodes rolling, it's so good
"Nothing in the dark" - I really like what they were trying to convey with it
"Purple Testament" - You know what's going to happen but just how rough it goes hits pretty hard
Alternatively, one episode I try to avoid anytime it comes up
"Spur of the moment" - The lady screaming at the start just makes me uncomfortable. Really uncomfortable. Like difficulty sleeping uncomfortable. I can't quite explain it because I know what happens in the episode and it shouldn't be that way, but it is.
My favorite has always been "Walking Distance". The guy goes back in time to when he was a kid. Reading history it certainly seems like things were calmer back then.