I think some of the best DLC I've played have been:
- Assassins Creed: Freedom Cry
- Batman Arkham Origins: Cold, Cold Heart
- Last of Us: Left Behind
- Batman Akrham City: Harley's Revenge
- Infamous: First Light
- Kingdoms of Amalur Reckoning: Dead Kel
What's your favorite/best DLC you've played?