The best television espisodes

The Sopranos - Pine Barrens

different strokes, when dudley got molested.

A mix of good shows and terrible shows:

Doctor Who - fun - Stolen Earth/Journey's End (end of season two parter)
Doctor Who - serious - Vincent and the Doctor
DS9 - In The Pale Moonlight (honourable mention Far Beyond The Stars)
The West Wing - Two Cathedrals (I've always liked 2162 Votes, The Supremes and Lift Off as well though)
Rome - The Spoils
Deadwood - A Lie Agreed Upon, Part 1
Six Feet Under - Series finale (mainly for the last 10 minutes)
The Wire -Allof season 4
Stargate Atlantis - The Shrine

Futurama - Amazon Women in the Mood.

Death by snu-snu!

Seinfeld- The Butter Shave

community - modern warfare (paintball)
lost - episode 1 and pennys boat
breaking bad - the one with the gus flashback
south park - scott tenorman must die
24 - first season finale
simpsons - monorail
dollhouse - the dvd only "future" episode
shield - finale
futurama - jurassic bark
curb your enthusiasm - seinfeld crossovers
seinfeld - masturbation contest

Spartacus: Blood and Sand season 1 finale - Kill Them All

Always Sunny - DENNIS system

Dexter - The episode where Lyla kills Doakes

IT Crowd - The Work Outing.

First two episodes of the second season of The West Wing immediately come to mind.
Many Lost episodes the first three seasons are favorites too.

TNG - All Good Things

Anyone?

Game of Thrones - Blackwater
Breaking Bad - Ambushed
South Park - Scott Tenorman must die

I can't say because it hasn't been broadcast yet.