Fallout: New Vegas, in which case there's really no good reason not to get the free mod Autumn Leaves when it becomes available tomorrow.
Autumn Leaves has been in development for four years, and it shows, with eight quests spanning seven to ten hours, multiple endings, more than 2,000 lines of voiced dialogue, and its own original soundtrack. Think of it as unofficial DLC with a chunk of story related to but separate from the rest of New Vegas.
The setting is "a derelict library inhabited by sentient machines, each with their own back-story and agency", and apparently it features "excruciating dilemmas" and "philosophical themes", all of which makes me imagine something like romance like we nearly had in the base game.
(Thanks, Eurogamer.)
