I do know, but even so you can turn it off in many games. I like to have the least amount that is possible.
Actually you cannot. All console FPS's have a back end style of aim assist. Its not as obvious as the toggle aim assist but its there.
Except from game informer explaining the different types.
SNAPPING
Early first-person shooters on console struggled to make aiming feel intuitive and rewarding, since it was impossible to match the accuracy and speed of the PC's mouse interface. Snapping (also sometimes called auto aim) was the earliest solution to cnosole control problems. Titles like Rare's GoldenEye 007 aided players by reorienting their gun barrels toward enemies whenever a player's crosshairs were in proximity of their target. It wasn't a flawless system, but it helped make shooters more accessible for console owners.
ACCELERATION
Many modern FPS also have highly tuned acceleration curves for reticle movement. When a player pegs their aiming stick in one direction his or her reticle will start moving slowly in that direction before picking up speed. This is noteworthy because it makes aiming at nearby targets easier without significantly sacrificing a player's ability to make quick turns.
FRICTION
Bungie introduced friction in the first Halo, and nearly every shooter uses it today. A simple way to describe friction is that it slows a player's turn rate as soon as their reticle passes over an enemy, but that's not the whole story. "What we really do is slow your top speed, and then dramatically decrease the rate at which the crosshair will slow down when you let go of the stick," explains Griesemer.
MAGNETISM
Some games stop with friction, but Halo adds another system to the mix. Once a player has locked onto a target, and that target begins to move, magnetism helps players stay trained on that target.
Whether we want to admit it or not, we need the help. Console controllers aren't designed to move a crosshair across the screen with the kind of fidelity FPSes require. Aiming system are practically required from any FPS that wants to stay competitive.