While things like weapon specialization and similar help put the fighter a bit more in focus, if the GM feels they need a little extra help, here's a few suggestions suitable for most pre-D20 D&D editions as well as most any OSR game.
Due to their hardiness and training, for the first three levels of experience,the fighter may roll their hit dice twice, picking the better result.
Weapon of choice:
At level 1, the fighter may select a single type of weapon as their weapon of choice. When attacking with a weapon of choice, apply a +1 bonus to attack rolls. Weapons of choice may be switched with each level of experience.
When at (or reduced to) less than 10 hit points, any hit taken will cause 1 less point of damage to a minimum of 0.
When knocking down doors or performing other feats of strength, the fighter gets a second attempt immediately in the same round, if the first attempt fails.
Any level where the fighter rolls a 1 or 2 for their hit dice, they may add an additional weapon proficiency to their total.
Let me know in the comments if you have other suggestions or ideas.
Of course, if you think fighters are totally fine as they are, let me know that too!
Thing of the day:
If you use miniatures, sometimes it's fun to simply get a little pile of random beasties to pick from. On occasion, a miniature have inspired me to include a critter I'd rarely use otherwise.