There's a keybind in Call of Duty: Black Ops 4 that centres the camera. Assuming you and an opponent are on a level plane, a centred camera in Black Ops 4 rests on their head. And then there is a gun – the Mozu – that can kill in a single headshot, if paired with the Skull Splitter operator mod.
This all adds up to a pretty powerful exploit. To see just how powerful, check out the video embedded below. As you can see, the player only needs to worry about aligning themselves horizontally with their opponent – given this, they can snap instantly to head height and score a guaranteed kill. It's quite something.
The video is courtesy of Redditor JollyRogers1503, who posted a PSA to the BlackOps4 sub after what I can only assume was a pretty unpleasant game on the receiving end of this exploit.
As you probably know, centre-view is nothing new in action games. I remember it as a helpful feature to get your bearings in six degrees of freedom shooters like Descent, or stop the environment stretching in 2.5D engines like that which powered Dark Forces. Animol points out that it's been in Call of Duty “since forever” too, going back to at least the first Modern Warfare.
So it’s a bit of a surprise no-one thought to exploit it before, to be honest. The option is just there in the ‘on foot’ section of the keybinds menu.
Clearly some action is needed – one sensible suggestion on Reddit is to introduce a short delay to the camera correction so you can still centre your view, but not so quickly as to provide a winning advantage in gunfights. Until then… I dunno, crouch?