Quickleaf
Legend
On a generic class level, the only thing I could see would be a bonus to Athletic things. The Fighter base class is so generic as to be usable for a variety of character types. This leaves customization to backgrounds/skills, plus feats (if available).
I could see several out of combat benefits dedicated to specific sub-classes, however. A cavalier with bonuses to riding and/or followers. A knight with bonuses to social interactions. A brute with bonuses to intimidation and interrogation. A scout with bonuses to hiding and perception.
1. The Gear Guy: I recently finished watching Matthew Colville's History of D&D One Fighter at a Time, and he does a great job (with the possible exception of leaving out several traits from the OD&D fighter).
One thing he reminded me of was how AD&D's %Strength dramatically boosted weight allowance, how the fighter started with more gold than others, and how the fighter used to be the only one who could use magic swords. So an argument could be made for the fighter (sans subclasses) being the "gear head" or the "burden bearer." This was stripped out of the class, however.
2. The Prestige Guy: The fighter used to become a baron, collect taxes, and get the most numerous and best followers. Moreover, in OD&D the experienced fighter could scare lesser goes simply be virtue of reputation or force of personality. So an argument could be made for the fighter (sans subclasses) being the "prestige guy." This was stripped out of the class, however.