Spoilers
“Clyde Bruckman’s Final Repose”

This is one of the best X-Files episodes of the entire run. Clyde Bruckman’s Final Repose starred Peter Boyle as a grumpy man who has the psychic ability to see how individuals are going to die and he finds himself stuck in a murder investigation of a serial killer who is targeting psychics.
One of the greatest lines of the entire series was in this episode.

From IMDB:
- Clyde Bruckman: You know, there are worse ways to go, but I can’t think of a more undignified way than autoerotic asphyxiation.
- Fox Mulder: Why are you telling me that?
- Clyde Bruckman: Look, forget I mentioned it. It’s none of my business.
Peter Boyle was absolutely perfect in this role, a down-on-his-luck insurance salesman who has been beaten down by life and by the visions of death that he sees. His sarcastic and snide remarks were extremely funny and were delivered beautifully. His chemistry with David Duchovny and Gillian Anderson was tremendous.

Though there was some wonderful humor in this episode, it was also one of the darker episodes of the season. It blended the two tones together seamlessly.
Oh, and Bruckman indicated that Scully was not going to die, a quip he made that was carried through the series.
Definitely this is one of the best episodes of the show and one of the best episodes of TV of all time.