I was much more into the 1950s Twilight Zone, but I distinctly remember the episode entitled "The Card" really freaking me out as a kid. I was only about 6, and the whole reposessing part where the bank began taking everything away from the lady scared me pretty bad.

How has no one mentioned The Hellgrammite Method from Season 3?

Cool thread.

The invisible man episode

The Elevator
Two brothers search for their missing father, a mad inventor. In their search, they find a trail of abominations caused by his invention.
2.
Devil's Alphabet
In Victorian England, a club made up of Cambridge alumni swear to honour an oath to continue attending their guild meetings even after death.
3.
The Burning Man
Set in the 1930s, a traveling woman and her young nephew pick up a hitchhiker who babbles crazily about evil, rebirth, and the unquenchable hunger for, amongst other things, human flesh.
4.
The Uncle Devil Show
A neglected boy watches an "interactive" television show.
5.
The Shadow Man
A meek and fearful teenage boy finds a malevolent shadow entity lives under his bed.
6.
Gramma
A boy is left home alone with his creepy bed-ridden Grandmother.
7.
Need to Know
Insanity spreads in a small agricultural town.

Who are you carrying all those bricks for?

Here are some of my favorites (all from 50s and 60s, though):
Third from the Sun, The Hitch-Hiker, The Four of Us Are Dying, The Fever, Mirror Image, The Monsters are Due on Maple Street, Nightmare as a Child (one of the creepiest), After Hours, Eye of the Beholder, Twenty-Two, Will the Real Martian Please Stand Up (one of my all time favorites), The Arrival, Little Girl Lost, Nightmare at 20,000 Feet, Living Doll, Number 12 Looks Just Like You, Stopover in a Quiet Town, The Masks. Just to name a few. Happy watching.

those 3 are my favorites. and I think there was one other; 'Something in the Walls.'

The Uncle Devil Show is 6.25 minutes of pure creepiness.
https://www.youtube.com/watch?v=lp1h2ioDHQk

Nightcrawlers (William Friedkin rocks!)
The Shadowman (Great punchline)
The Elevator (It's just short and fun, and it stars Stephen Geoffreys from the original Fright Night)

A Little Peace and Quiet and Examination Day are to me the creepiest episodes. I also thought A Small Talent For War was pretty creepy.
The one that really haunts me as an adult now is Little Boy Lost. (KINDA SPOILERS)
Since I've seen that I haven't been able to look at menstruation the same way again!
SPRING BREAK FOREVER BITCHES!

The Toys of Caliban is sad. A special needs child with powers to bring things to life and you have to protect him.
Acts of Terror is inspiring & scary. Being abused is bad enough. But having a dog figure come to life and put a stop to it can drive you crazy.
A Little Peace and Quiet is creepy. Wanting to have peace and with the threats of nuclear war.
The Misfortune Cookie is creepy. The old story of the critic who gets what's coming to him. Made worse with the desire for food. Makes you not want to eat.
Examination Day is sad. Shows part of what it will be like with a country incharge of a persons every move.
Many, Many Monkeys is the most realistic one. With outbreaks going on since the beginning of time and the caretakers not being caring. Some that have a heart end up being effected greatly.

I saw the episode "Gramma" on TV when I was about 9 or so. That night is the only time I can recall sleeping in my parents' bed in my entire childhood.
Gently With a chainsaw

The ending to "Examination" was creepy , disturbing and sad all at the same timeShadowman was creepy but in a fun way.

Shadow Man and Nightcrawlers
Miskatonic University - Go Pods !!!

For me it has to be "Gramma". Unsurprising that it was based upon as short story penned by iconic horror maestro Stephen King.

In addition to the ones mentioned, "The Elevator."
"Passion is just insanity in a cashmere sweater!"

"The Uncle Devil Show" - not scary, but I found it pretty creepy.
-Goodnight, mother of six!
-Goodnight, father of two!

"Nightcrawlers" scared the hell out of me.

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"Gramma" and "The Shadow Man" are very creepy. I didn't see them until I was in my twenties and they scared the heck out of me!

Nightcrawlers, Kentucky Rye and A Little Peace and Quiet are particularly creepy