The crossbow is very silent and can be very effective weapon in the right hands. For example as you know crossbows are often used for hunting. Crossbow arrow can carry explosive tips and can create confusion in the enemy because due to the silent operation you cant understand from where it comes. A lot of special services and special operation units on higher level are using for example pneumatic weapons with poisoning pellets. It can guarantee you silent operation again. For example the cyanide can kill you in less than a minute. Thats if the arrow dont do the work by itself.