My favourite fighter would be... my current character, Borivik. It is a Human Battlemaster of the FR. He is a folk's hero, because he leaded a revolt against an oppressive church in its native land. He's an atheist after encountering another of my fighters, the original Gastón, a mercenary and merchant obsessed with bringing down the gods, which he sees as powerful, tyrannical monsters. Nevertheless, Borivik and Gastón are two worlds apart in concept, other than belonging to the same subclass. While Gastón is an old (it is bordering 40 years old in a world without toilets), wise and calmed soldier and mercenary with a knack for weapon's business (he sells his weapons of choice: crossbows of every type), Borivik is a very young, very hot-blooded blacksmith's apprentice (19 years old). And he is strong.
I builded it by rolling dice, with awesome luck. At level 3, he has Str. 18, Dex. 11, Con. 16, Int. 14, Wis 14 and Cha. 14. He has the Shield Master feat, so he has at least +2 to every save, and fights with a longsword and a shield He uses a chainmail, and he has proficiency on Athletics, Survival, Investigation, Animal Handling and Intimidation, and he knows how to use blacksmith's and cartographer's tools. He knows the following maneuvers: Precision, lunging and sweeping attacks. He uses extensively his crowbar, his smithy tools and his shovel (to dig holes, mostly), and like to throw torches on Giant Spider's caves.
His personality is convoluted. He is on the run from his ancient enemies: the nobles and church members. He is brash and insolent, but good-hearted and responsible. He is also an alcoholic, prone to risk the success of a mission for a bottle of wine, a thing that he denies (this is his flaw). But he is responsible for its actions: he was prone to sacrifice himself after the Storm god attacked the ship in which he was (well, not really sacrifice, he carried a big barrel with its equipment when he jumped of the ship). He did it because he comprehended that Talos was after its party after they desecrated its temple in Atkathla, killing the high-priest and saving the poor captive to be sacrificed.
To do that, he devoted himself to reading about Talos, and entered in a brawl at the Copper's Crown to be noticed by the talosites as an adept. And he won every fist-fight, grabbing its rivals and bashing their heads against the bars. When they entered in the temple in disguise, he grabbed a bottle of wine and jeopardized the mission. But then he saved the party twice, even at his arm's expense (dislocating its shoulder to rescue the other -dexterity- fighter when he fell off the rainy tower and catching the falling warlock also); he also single-handledly shut down the high priest, when the tabaxi monk fell for a Guiding Bolt: run against him and shoved it with its shield, and then grappled his mouth with its attack (at disadvantage, but I'm great, so, yeah: no verbal components to you). In other adventure, he broke a crypt's gate with sheer strength, fight and defeated most of the Giant Spiders, and then overkilled them by setting their lair on fire (I don't need a wizard when I have a torch and oil). He also maintained a ship's mast by hulking all its strength on the task, and saved his companions when finally the ship sunked. He was also the only one to have all his equipment, because he could carry a big barrel. He also digged the graves of a phantom town, and made CPR to a drowning NPC.
Borivik is the big guy. He is the reliable one, the most powerful in the party (although the monk is quite a beast), and overall the most versatile. He doesn't really need Thieves' tools to open a chest: he can break the lock with its tools, or simply with its massive strength. He don't really need the warlock to kill a lot of little enemies: with his shield, action surge and sweeping attack he does it just fine. He don't really need the bard's healing: he got his Second Wind and Hit Dice, and its shield and armor to protect him from harm. He can swim, climb, grab, lift, fight, resist and open anything like a pro. I'm in love with my character.
