Long ago, I read that no one has ever been documented as having been killed with a thrown knife. I don't know if it's true, but I also can't think of anyone who was killed by a knife-thrower. So if someone is killed with a thrown knife in your story, at least one reader will slow down there.
I'm looking at you, Dashiell Hammet. I'm halfway through Red Harvest, and I was loving it right up to the thrown knife. But that was just a bump; I'll keep on reading.
ETA: Karen Conlan provided this link: Myth: Deadly Throwing Knives : Escape Pod