A crucifix? Holy water? Silver bullets? Incense? Salt? Garlic? Pepper? Olive Oil? Ciabatta? Ok, maybe I'm a bit hungry, but no. None of these are good weapons against ghosts.

The best weapon against ghosts is: Occam's Razor!

So keep in mind, the next time you see a ghost, grab Occam's Razor and cut deep into the ghost. Aim for the head or the chest of the ghost and make sure your cut's are deep enough. If you only scratch it, the ghost might get angry and become a lot harder to hit. That happened to me once, and it was quite a mess. In that situation, it might also be helpful to use Newton's Flaming Laser Sword, but that douchebag Mike Alder won't lend it to me anymore, after I might have stabbed Plato with it a bit by accident.

Panel 1:
G and H are in a dark room, a spirit box is in front of them, beeping.
H: I don’t think I like this. I’m super scared! Please, let’s go home!
G: Oh, don’t be lame! Ghost hunting is fun! Just watch. ahem GIVE US A SIGN!
Panel 2:
With a loud Fwooosh, a traffic sign appears, labelled in a strange language.
Panel 3:
H: Whaa ... what does it say???
G: I don’t know, I don’t speak sign language.