User blog comment:Pastawriter/I need help/@comment-4750363-20150617031826/@comment-25428589-20150617145000

Just because something is a cliché, doesn't mean you can't use it. If a knife makes sense in the situation, it's far better to use it, even if it is cliché, than, as Reading said, forcing a random weapon into the situation.

In all honesty, the weapon that's used isn't important. If you're worried about being compared to Jeff the Killer, Clockwork, etc, move your attention away from the weapon being used and onto the characters. What will set your story apart from them, if it is about some kind of serial killer, is the inclusion of believable characters with realistic motivations (as well as a good plot, good writing style, etc). The weapon's an afterthought.