Well, if i am play a catholic faction, i always use the inqusition weapon as a natural (religious) killer. And i use the grand-inquisitors as assasins, even better them. Because the assasins can be caught easily but they can hardly be killed by an assasin. And they do (inqusite) for the church :D
Anyway, while i am playing as Sicillians, i had a great (8 star) grand-inqusitior, he had killed so many generals and kings. Even i erased the Aragon royal family with him and aragons were eliminated. And i wonder if i could use him to his boss (the Pope). I wonder if a member of the church could kill the boss (!) of the church. As we know that, after you had put him on a general, there are two choices, he could be killed or live. But if he's alive, he could get a vice or virtue. After an inquistion sometimes, they will be too religious (gaining the vices which increases the piety) that you can't kill him with an inquisition. But sometimes they could get the bad vices (being like an atheist which deletes all piety point :) ).
Anyway after this explanation, i put my grand-inquisitor on the pope, and he couldn't be killled. I say "normal ". After i put him on him several times, he got the piety decreaser vices. i say "what? " And at the end he got the atheist virtue. I say ".uck! " But how? How can a Pope be atheist? I asked these questions many times to myself. But no answer, and i thought it could be just a bug of the game. And after one or two turns, the Pope (which always had wanted the catholics start a crusades against to me) buried on the cross which makes me feel good and laugh :)).
Thanks for your replies for now.