I am playing, as well as about to start DM'ing a one shot, in fifth edition D&D and one of my soon-to-be players has talked to me about making either a Fighter (Samurai) or Monk (Kensei) and was wondering if there was any feat that acted like the Bard's "Expertise" class feature but for weapons rather then skills.
While I have found some homebrewed content for this, I haven't found anything official, but I just might not be looking in the right places. Is there something like this or at least a homebrew that is relatively balanced?
Edit: Rather then adding the bonus to attack roll I was looking for something that just effects Damage even if it was a just 1/rest effect. I know that "Great Weapon Master" effect is a -5 to hit, +10 to damage. But I was hoping that there was something like, all attacks deal x2 Proficiency Damage for this turn, 1/rest, so the "Arthur the Archer" example wouldn't effect his to hit chance just the damage he deals IF he hits.