The X-Files came up in another thread. The XF Christmas special with Ed Asner and Lily Tomlin came to mind right away, so I guess I would have to list it among my favorite episodes. A tongue-n-cheek take on Tomlin and Asner as ghosts [previously married] who convince Mulder and Skully to shoot one another, on Christmas. Star Trek TOS: The Corbomite Maneuver West Wing: The Josh "Lemon" Lyman episode - The U.S. Poet Laureate- was right up there for obvious reasons. This is where the Deputy Chief of Staff makes the mistake of engaging an internet political forum dedicated to him, using his true identity.