If Barbarian is a class, and not defined by a Rage mechanic, then what is the Fighter?
Should the Fighter then be redefined as "Soldier" or "Man-at-arms"?
Part of the issue here is that backgrounds as separate from classes fit somewhat oddly with classes that have strongly implied backgrounds.
In the Dragon Quest series, the class that best matches the D&D Fighter best is called Soldier. The name "Fighter" is instead used for basically the Monk class.
I've always preferred "Berserker." It's not political, I just like it better.
I don't like Berserker for the same reason I was happy when Thief was renamed to Rogue in 3e. I don't want players thinking that Berserkers have to go berserk all the time or that they can't think rationally. It's bad enough as it is with people thinking Ranger = Archer because it has the word "range" in it.
Somebody mentioned battlerager up thread, and that’s now my current favourite.
I like this one, too, in spite of my reservations. I don't want the class's core ability to be in the class's name. It'd be like calling the Sorcerer the Fireballer. But I do like Battlerager.
I started going through 3.5e Presitige Classes (Bear Warrior, Tempest) and 4e Classes or Paragon Paths (Warden, Wildrunner) looking for inspiration, but they're not really generic enough or don't fit the flavor quite right. I think Tempest would work.
Edit: Actually, I think I just don't want Rage to be called
Rage. I don't like that it's flavor is about getting getting angry. I think it narrows the class scope. Obviously, yes, in actual play you can ignore the description in the book and call it Battlesense or Super Saiyan or whatever. I'm just not a fan of the default flavor of the ability, partially because of the cultural assumptions it packs along with it about what we civilized folks think barbarians are, and partially because I don't like telling new players that there's a class whose schtick is getting super angry. "They've got a bad temper," isn't a very fun or cooperative personality trait.