Halfway through DS9's "Hard Time".
One of my favorites. It's a classic sci-fi storyline with installed memories. It covers a lot of philosophical ground and a little psychology (this is what it's like to have delusions/hallucinations). While I tired of O'Brien's sharp tone over everything, the ending is great. It adds another wrinkle to Bashir/O'Brien's relationship (the friendship has a purpose). Like I said, one of my favorites.