There are quite a few different weapons in Rainbow Six Siege, and until players become experienced with this game, it's going to be pretty tough to tell which weapon is good and which needs to be left behind. The huge skill gap in Siege is partly the reason for this. No matter how good a player's weapon may be, other players are just going to be winning gunfights against them because of their knowledge of the game. That doesn't mean that the weapons absent on this list can't be perfectly effective, of course. But in a scenario where everything is even, weapons on this list are likely to win out against weapons that aren't.