These would be my picks.
Mash - Radar informs us Col. Blakes chopper went down
Dr.Who - Van Gohh at the museum
Futurama - Digging up his Nephews grave
Futurama - Jurrasic Bark
That Mash episode destroyed me as a child. It took decades for me to trust the TV again.
Then the Jurassic Bark incident happened, and I will never trust the TV with my emotional well being again.
Honorable mentions:
Scrubs - Dr.Cox looses his shit
Edit:
Just remebered this one Fresh Princes father ditches him
I couldn't think of any at first, but the MASH one is great. I remember they didn't give the script to anyone until right before they shot the scene, so as to try an illicit a genuine reaction from the actors before shooting (what are they, amateurs?). The first take was scrapped due to technical difficulties, and the second take is what made it in. They considered shooting it again because of the object falling onto the ground shortly after Radar leaves the room, but elected to keep it.
I'll try to think of some and get back to this.