The BioShock Infinite "Burial at Sea" Downloadable Content is some of the finest expansion content I've ever played in a game.
The first time I played this I was taken aback by the emotional toll it imposed. The second time (this video recording) - I noticed so many minute details that betray events that will occur later in the episodic content.
It's an excellent ending to an even better game; and something definitely worth playing, or in this case, watching.