for real... are all the weapons in the game useful?

A lot of guns do have their uses, certainly moreso now than older versions of csgo but some guns are too but to justify using e.g mp5sd when you can use mp9 and personally the ONLY pistol I ever buy is a deagle. Personally the one tap potential at all ranges and the two body shot kill (as bm as it is) is too good to give up for inaccurate dink machines.