the 
kartika is a 
ceremonial weapon used in some rituals to cut the bonds of ignorance, in other rituals to chop up demons.  It is used in conjuction with the 
kapala (actually made of a person's top half of the skull! 

 ).  I will upload pictures of the one I have in a day or so.
Another note: the phurba in some ceremonies is used to pin down the demon or evil spirit so the lama can have more control.  Sometimes you will see a horse head on top.  It is the form of a deity that frightens demons (the name escapes me at present).