OMG I love you for starting this thread!
Hehe. Ok, here goes, but I'll have more than 5 I warn you...
In no particular order because I can't decide:
1. Pusher. How can you put a man on trial for murder when he didn't actually touch any of the victims? Robert Modell "pushes" his will on others to make them commit suicide, and plays a game of clues with Mulder to lead him to him, resulting in a game of Russian Roulette.
2. Bad Blood. A new take on the classic vampire story. The story starts with Mulder staking a pizza delivery boy, only to find his vampire teeth are fake. A humorous episode, told twice through Mulder's POV and the Scully's POV.
3. Unruhe. Gerry Schnauzer sees demons. He looks into ppl and believing he can see demons in their heads, alleviates the problem by carrying out surgery, badly. When he gets near photographic film, the film is affected by his thoughts, like psychic photography, and the demons he sees appear in the pictures he takes of ppl.
4. Small potatoes. Another humorous episode, with a character who can alter his appearance to look like anyone, raising the question of whether we are who we are because of others perceptions of us.
5. Squeeze. Eugene Victor Tooms who can squeeze himself into small places. He kills victims for their livers, before going into hibernation.
6. How the ghosts stole Christmas. As mentioned above, the Lily Tomlin/ Ed Asner episode. I love the revolving rooms sets. A very traditional ghost story feel to it, as the ghosts attempt to talk Mulder and Scully into committing suicide as part of a loverys pact.
I could go on, there are so many I love.