There are two kinds of first person view – traditional and true.
“Traditional” First Person
The players in-game view is set at fixed heights and rotates around a central axis. While the the player characters arms and weapon are visible, these are representations only and do not match their actual location. In most modern games, the player characters body and legs are also shown, but like the arms and weapon, are only representations.
Examples: Counter-Strike or any Call of Duty, Halo or Battlefield game.
True First Person (aka ‘body awareness’).
The players in-game view is matched to the character models eye location. Different parts of the player characters model are visible depending on where the player is looking and what action they are performing. This is the actual model, so the location of the players arms and weapon is the true location, not a representation.
Examples: Operation Flashpoint (original), ArmA 1/2/3.
Aside from the added degree of realism, a true first person view helps bring players into the game, simplifies all interactions and eliminates several flaws inherent to the FPS genre:
- Poor, missing or unsynchronized models, animations, sounds and effects.
For example, from your perspective you are in the middle of a long and complicated reload animation, complete with sounds.
To everyone else, you appear to briefly tilt your weapon and move your left hand to your hip and back up again. - Inability to effectively use stealth based tactics.
For example, you stop short of a corner of a wall, thinking you are perfectly hidden. To everyone else, your weapon and arms are sticking out beyond the wall in full view. - Inaccurate and/or unbelievable weapon trajectories.
For example, an enemy is leaning around a corner and with only their head visible; yet somehow they are shooting you.
Performance issues are a moot point, since a lot of modern FPS are including a first person view of the players body and legs anyway.
Player animation are also a non-issue, as the time saved in not making two versions – a first and third person – of weapon models and animations can be put into this.
If you are creating a first person shooter with a humanoid based protagonist, there is no reason not to use a true first person view.
Kris Redbeard 
This is spectacular Kris! Bravo.
My new Favourite Redbeard!
really alazing, can i use it for my game?
I am implementing a true FPS camera on my game project, but running into some issues, first of all, i have disabled the mesh to prevent any clipping, but still, the camera has to be in place on the neck joint, otherwise when a character runs for example, and the body is tilted forward, you could see the back of the character, and if the camera is attached to the neck, it results in jerky camera movement with any normal animation, so im thinking either redo the animation to where the neck join is always stable, or keep the camera detached and compensate the position with code, any input?
Clazzid
Dont know why i didnt type the word “Head”, i disabled just the head mesh. to prevent any clipping
I agree with a lot of this, but it does ignore some of the complexities of setting this up in a nice polished way. If one is creating a fast moving game with exaggerated animations you have to stabilize the camera in some way. If the camera is synced with the mesh eye position it is going to be doing everything the world mesh is doing. If for instance you strafe and stop and play a realistic pivot anim the camera is going to have to either desynch with the world mesh or do some jerky movements that are likely not good for fast gameplay.
So you either have to create some kind of complex full body ik system, limit your animation style, or desynch for things like this. I think it comes down to the game you are making.