10. Pilot

9. War of the Coprophages

8. Humbug

7. Tooms

6. Gethsemane

5. Zero Sum

4. Hollywood A.D.

3. Die Hand Die Verletzt

2. Jose Chung's "From Outer Space"

1. Clyde Bruckman's Final Repose

via thatguywiththeglasses

10. The Artificial Intelligence in Kill Switch
9. The Chameleon-like Forest Creatures in Detour
8. The Jersey Devil in Jersey Devil 
7. Big Blue in Quagmire 
6. The Parasitic Arctic Worms in Ice
5. Eugene Victor Tooms in Squeeze and Tooms
4. The Flukeman in The Host
3. Donnie Pfaster in Irresistible and Orison
2. The Black Oil
1. The Cigarette Smoking Man

via yesbutnobutyes

10. CCH Pounder in "Duane Barry"
Airdate: 10/14/1994

9. Michael McKean in "Dreamland I" (11/29/1998) and Dreamland II"
Airdates: 11/29/1998 and 12/6/1998

8. Lili Taylor in "Mind's Eye"
Airdate: 4/26/1998

7. Nick Chinlund in "Irresistible" and "Orison"
Airdates: 1/13/1995 and 1/9/2000

6. Bruce Campbell in "Terms of Endearment"
Airdate: 1/3/1999

5. Veronica Cartwright (Various Episodes)

4. Doug Hutchinson in "Squeeze" and "Tombs"
Airdates: 9/24/1993 and 4/24/1994

3. Brad Dourif in "Beyond the Sea"
Airdate: 1/7/1994

2. Peter Boyle in "Clyde Bruckman's Final Repose"
Airdate: 10/13/1995

1. Steve Railsback in "Duane Barry" and "Ascension"
Airdates: 10/14/1994 and 10/21/1994

via stars.ign