While this could change I think I'm going with "Twilight Zone"'s "Shadow Play." It's amazing how much they pack into that episode's twenty-four minute running time. The last twenty-minutes or so of "Twin Peak"'s season two finale would also be up there (the rest of the episode is pretty "meh").
The live episode of The Pinky Lee Show, where ex-vaudevillian Pinky had his celebrated, live, on-air heat attack. It was a Saturday-morning kids’ show. Pinky would emerge in a black-and-white checkerboard suit and Homberg hat, do a soft shoe, and sing, “Yoo-hoo, it’s me. My name is Pinky Lee.” On this particular day, it went, “Yoo-hoo, it’s me. My name is GAAAKKK!,” followed by Pinky crumbling to the floor. Suddenly, there was a guy wearing headphones, close-up, on camera, identitying himself as Uncle Mike, and telling us kids that we were going to be watching cartoons for the rest of the show. In the background, I could clearly see a guy pounding on Pinky’s chest. Then we saw him being unceremoniously dragged off the stage by his feet. If you consult Wikipedia, it will say that this was an asthma attack. I saw the event. You don’t pound on an asthma victim’s chest. Wow. I miss live TV. Except for NBC’s pathetic Christmas live Broadway productions.
Not unlike the wresting (episode) where Owen "The King of Hearts" Hart augered in from 50 feet after becoming disengaged from his gear. The show went on, blood stains in the corner of the ring living proof that after all it wasn't fake.
On YouTube there's footage of comedian Tommy Cooper dying of a heart attack in front of an audience who clearly think he's trying to pull one over on them.
You can’t beat live TV. When someone has the guts to do an offshore show of people being fed to starving lions, we will
have our new Number One broadcast TV show, brought to you by Toyota, McDonald’s and Google.
That episode in "The Walking Dead" ---where the black guy is bitten on the arm in a house. It happens lickity split...the group grabs him and they take off in a sedan. The money shot is from distance as the car climbs an incline. The car stops, all four doors open simultaneously and he's taken out and laid upon the road. They didn't want him to turn in the car. They had no choice but to take him out.
The episode ends with the reverend's voice reciting this:::
We look not
at what can be seen,
but we look at what
cannot be seen
For what can be seen
is temporary,
but what cannot
be seen is eternal
For we know that
if the earthly tent
we live in is destroyed,
we have a building
from God,
A house not made
from hands,
Eternal in the heavens,
In the heavens
- "I invite each of you to sit down in front of your own television set when your station goes on the air and stay there, for a day, without a book, without a magazine, without a newspaper, without a profit and loss sheet or a rating book to distract you. Keep your eyes glued to that set until the station signs off. I can assure you that what you will observe is a vast wasteland."
- FCC chairman Newton N. Minow - 9 May 1961
He didn't know shit from apple butter. This thread is living proof.
I recall another great episode. This one is from "Leave It To Beaver." It's from quite early in the series.
An itinerant guy (Andy) talks Ward into letting him paint the house. He's alcoholic. June doesn't want him around the boys but Ward insists. They have to go out for the afternoon, leaving the boys at home with this guy. He cons them into letting him into the house where he gets hold of a bottle of booze. He gets drunk. We're not shown this. The parents come home and find the situation.
The next day Beaver is sitting on the curb playing in the gutter with his sail boat, it's been raining so there is water in the gutter. He's humming "Clementine" which is themed in this episode. "Andy" happens by and sits down next to the Beaver (in the gutter)...tries to explain to him what happened and how sorry he is to have presented himself to the boys in that state. "An empty bottle goes along with an empty life." He confesses to the boy. He vows to return to the Cleaver house and finish the paint job. Rises and ambles down the street as Beaver returns to his play in the gutter, humming the tune till the fade out.
It was a good show. Despite the parents being two-dimensional, it was a leader in being the first show in my recollection of showing kids in a far more realistic way than any other of its kind.