So, I picked up Season 1 of X-Files this weekend since the sets have finally dropped to a reasonable price (I wish there were more extras, but at $34.95 for 24 episodes, I can overlook it). As I watched it, I realized that some of the strongest eps in the entire series can be found in that season and that Carter established the basic structure of the show within the first 3 episodes.
This got me thinking about stand-alone episodes: shows that can be watched without ever having seen another episode and yet provide a complete story. So my question is, what are some of the best stand alone episodes you've seen? In other words, you could show these episodes to someone who has never seen the show before and hook them on the series little to no explanation of ongoing subplots and character development.
Since X-Files started me down this road, I'll start with that. The show has two basic episode structures: "mythology" episodes, which serve to further the central plot of alien abductions and government conspiracies, and "monster" episodes, which have Scully and Mulder hunting down the freak of the week. I picked one of each from the first season.
Ice: A brilliant homage to John Carpenter's The Thing, in which Mulder and Scully are trapped in an arctic research station investigating why the team originally stationed there went bonkers and started killing each other. The paranoia is absolutely palpable, combined with a real sense of isolation and desperation. Easily one of the best hours of television I have ever seen.
E.B.E.: M and S attempt to track down the government's secret transportation of an "alien" in the back of a non-descript 18-wheeler. Not only did this episode introduce supporting characters who would become an important part of the series (The Lone Gunmen), it also turned Mulder's relationship with Deep Throat completely on it's head, leaving him to wonder if he could trust anyone other than Scully. The best part of the episode is that the final reveal not only doesn't answer any of your questions, it leaves you with a whole new set to ponder (such as which side is DT on and how much has what he has told Mulder in the past been outright lies?). While the show eventually became so convoluted that it disappeared up its own ass, this ep showed that the core concept had legs when distilled to its purest form.
Okay, your turn.

Chris McLaren