Single Player Survival FPS
Progression of Skill-
Skill is needed to preform tasks often given to you out of the gate in FPS. At the very beginning:
All guns are difficult to use. Pistols sway, and LMGs just about fly out of your hands. Guns like assault rifles will jam much more, and moving around with them makes this even more common- running about and sliding will make the possibility of a jam more prevalent. The best kind of ranged weapon to use, if you absolutely have to, is a bow or small caliber pistol. Melee weapons are considerably more useful but very very few are an instant kill and the more finicky ones (such as pocket knives) are slow to bring out. Fumbles are possible.
Movement is also difficult- certain actions cause injury (such as sliding down a hill), and you can't run fast or for too long.
At the start, you'll get points to spend in skills immediately. This allows you to have a small amount of natural ability.
For guns:
You first have to put experience into using pistols, revolvers, and bows. These types of weapons will show sharp accuracy increases and more controlled kick and recovery from kick and all movements involved will become faster (reloading, etc.), and accuracy for all guns will increase slightly. Pistol jams will be fixed more quickly, and happen less often (there is a point they will not happen.)
From there, you can begin levelling on Light Arms. Automatic weapons become viable at this point, and submachineguns and some assault rifles begin improving just like pistols, then large weapons like bigger ARs and LMGs. It takes a while before you can use an LMG with any effectiveness at all, but it is worth it.
For melee:
Here, there are less restrictions. You can level for Blunt, Blades, and Unarmed. Leveling weapons of their category makes them quicker, deadlier, faster to move with when sneaking, as well as unlocking abilities such as Beatdown (knock down a foe with a blunt weapon before finishing them off, or knocking them off a cliff), Jack Rip, which quickly strikes a foe multiple times to disarm them before slicing their throat, and the Stranglehold lets you take a human shield by coming from behind them and grabbing their necks, choking them. These takedowns give you more options such as attacking from on high or low, and warrant more XP.
For general abilities:
You also need to be able to heal yourself and move about the world. If you were to max out Movement, you'd be able to act like a tireless parkour machine, but if you start at 0, you won't even be able to slide without hurting yourself, and running is pathetic. You can't use a medkit without some skill, and with enough levelling you can heal yourself very quickly with minimal supplies. Even looting is determined by skill- at it's lowest, you won't be able to spot anything useful unless you're right up on top of it, then they start appearing on your minimap, before you gain the ability to mark items by looking at them (such as in Far Cry 3) and also be able to unmark them with the press of a button.
So, you start as someone with very little ability to take injury, use weapons, move or heal yourself, or really effectively do anything in the game. It makes you earn your skills.
Guns can jam. They can jam with different types:
Light: Something like the casing getting stuck halfway through ejection. This can be fixed by inexperienced players in a few seconds and nearly under a second for those with experience.
Medium: This is a bad jam that could take 30+ seconds for someone inexperienced to fix, if they even can without taking the weapon to a gun shop. Experienced players will take 10 or more seconds.
Heavy: Very bad jam. Experienced players will take 30 seconds or more to fix.
Critical: The gun is broken and requires maintenance.
Guns will jam more and more critically based on experience, as well as the gun. Some guns won't jam very often even in a noob's hands, some guns are annoying to use for even experts.