I'll show you how I made a keg tap for Halloween where you stab a head to pump the keg.

Step 1: Materials

You'll need:

Keg tap
Severed prop head
Butcher knife
2 coupling nuts (size may vary)
3" threaded rod (matches coupling nuts)
Red paint

Tools:

Knife
Grinder, sander, or sand paper
Welder or JB Weld
Zip Tie

Step 2: Head Preperation

Cut a hole in the bottom of the head large enough to go around the tap, and a hole in the top for the knife to pass through.

Remove the stuffing so nothing interferes with the pumps operation.

Step 3: Knife Assembly

First and foremost, dull the blade. We don't want real blood used for the project. I used an air grinder to do this, but you can use any method you'd like.

Next, remove the ball off the tap. Screw both coupling nuts onto the threaded rod, leaving enough room on one end, so you can screw it onto the tap.

Lay out your coupling nuts onto the knife, and secure to the blade either by welding or with JB weld.

Step 4: Final Touches and Assembly

Water down a bit of red paint so it runs and add on top of the head and to the knife.

Push the tap through the head and screw the knife onto the tap.
Use a zip tie to secure the head to the tap.

Tap the keg and stab the head!