I'm gonna have to say Knife of Dunwall/Brigmore Witches for Dishonored.
A bit overpriced perhaps but they gave you several new missions, each with their own styles and secrets, loads of new lore for one of my favorite worlds, an arsenal of new tricks and Daud, who is a glorious bastard. The entire story was well-done, each mission had multiple ways to win, the characters stuck out more than the main story, and it brilliantly sets up for Dishonored 2 in such a way that it's still a complete story and teases a possible future meeting with Daud and/or Billie Lurk in Karnaca.
Also I am unbelievably biased towards Dishonored...
A bit overpriced perhaps but they gave you several new missions, each with their own styles and secrets, loads of new lore for one of my favorite worlds, an arsenal of new tricks and Daud, who is a glorious bastard. The entire story was well-done, each mission had multiple ways to win, the characters stuck out more than the main story, and it brilliantly sets up for Dishonored 2 in such a way that it's still a complete story and teases a possible future meeting with Daud and/or Billie Lurk in Karnaca.
Also I am unbelievably biased towards Dishonored...