For my last two parties, I've had a Wheel of Torture that guests can spin for a "specialty" drink (see pic link below). Here are some of the drinks we did last year... these were all small shots, not really drinks to sip

The previous year we did a lot of test tube shots and cocktails with black vodka (Blavod).
Corpse Reviver (No. 2)
1 shot gin
1 shot Cointreau
1 shot Lillet Blanc
1 shot fresh lemon juice
Dash of absinthe or substitute (roughly ¼ teaspoon)
Shake well with ice and strain in to a cocktail glass. Garnish with a maraschino cherry.
Wicked Witch
1.5 oz. Whiskey
0.25 oz. Maraschino Liqueur
0.25 oz. Pineapple Juice
1 tsp. Lemon Juice
Silver Bullet
Peppermint Schnapps
Chocolate Syrup
(I thought about making this one just a shot of Coors beer, but I hate beer ;P)
Brain Hemorrhage
Peach Schnapps
Bailey's
Grenadine
(here are directions and pics:
Brain Hemorrhage Shot - Halloween Drink - pretty similar to the Alien Autopsy below. These drinks were favorites because they look gross but are pretty tasty)
Alien Autopsy
Mountain Dew
Bailey's
Grenadine
(directions on this page:
I Make Projects - A Cannibal-Themed Halloween Supper - slightly different ingredients & execution from the brain hemorrhage)
Zombie
Store bought Zombie Mix
Mad Scientist was bartender's choice... so whatever I felt like mixing up

And
Pick Your Poison was the guest's choice of any drink on the wheel.
Here's my Wheel of Torture from last year (a painted $7.99 lazy susan from Ikea)
http://www.halloweenforum.com/picture.php?albumid=1371&pictureid=17851