Most can cause serious injury to the eye. The BB guns that fire 4.5mm steel bbs can cause serious wounds. In extremely rare cases they can cause death if the muzzle velocity is high (500 fps or more) and the person is shot at close range. But death is rare because round BBs don't penetrate as good as pellets/darts.
https://www.quora.com/How-dangerous-are-BB-guns