I have a hard time narrowing it down to just one. Here are some of my favorites, a few of which have already been mentioned:
The Shield. As mentioned above, Mackey just sitting at that desk kills me. Still not over Lem's death.
The Sopranos. A perfect end to a near-perfect show.
Friday Night Lights. Love this show so much. Perfect ending.
Buffy The Vampire Slayer. Lord of the Rings-style epic battle at the end.
Star Trek: The Next Generation. Easily the most satisfying finale I've seen.
Battlestar Galactica (2004). Not a lot of people liked it, but I loved how it ended and the twist about Earth.
The Shield. As mentioned above, Mackey just sitting at that desk kills me. Still not over Lem's death.
The Sopranos. A perfect end to a near-perfect show.
Friday Night Lights. Love this show so much. Perfect ending.
Buffy The Vampire Slayer. Lord of the Rings-style epic battle at the end.
Star Trek: The Next Generation. Easily the most satisfying finale I've seen.
Battlestar Galactica (2004). Not a lot of people liked it, but I loved how it ended and the twist about Earth.