Human and those stats and hilariously broken. +2 Str and +2 Con with no stat penalties, 30ft movement and a free feat? Better than extra con given the downsides.
You'll chew threw literally anything. Just grab a two hander (go falchion. Damage dice means nothing with your insane static damage, but crits will be nice). Go invulnerable rager for extra damage resistance. Power attack your way to success.
For the fun of it, given for dexterity, take the trait highlander. You'll rock stealth tests, and as you'll likely be wearing studded leather for the full dex bonus, the trait will cancel out your ACP. So your stealth at Lvl 1 will be +9. That's really good. Also with Cha16 get the trait world traveler so diplomacy is a class skill. It'll get you +8. Having +8 diplomacy and intimidate makes you a great party face as well.
Go pure rager and get lesser beast totem, as the beast totem build means lots of AC at lvl6 and pounce at lvl6.
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You may also consider playing a monk/enlightened paladin with those stats. The paladin doesn't have the paladin code, but is instead all about self perfection.
Monk (1) gives you Wis to AC and flurry of blows. Enlightened Paladin (2) gives you 2 points of Cha to AC, Cha to saves and the ability to beat up one person each day really well.
At lvl3 without any equipment you have AC 20 (jumps up to an easy AC 23 with a bracer of armor, ring of protection and dodge). Your saves will be so high that there will be no reason to cast at you. Start using dragon style for 1.5 strength damage unarmed, and you can flurry for a second attack.
Save up for the gloves which add +1d6 acid damage to your unarmed strikes and an amulet of mighty blows. Laugh as you walk around naked, blocking swords with your chest.
It's a really MAD character. But all of your stats are at legendary levels. So why not make full use of it?
Human and those stats and hilariously broken. +2 Str and +2 Con with no stat penalties, 30ft movement and a free feat? Better than extra con given the downsides.
You'll chew threw literally anything. Just grab a two hander (go falchion. Damage dice means nothing with your insane static damage, but crits will be nice). Go invulnerable rager for extra damage resistance. Power attack your way to success.
For the fun of it, given for dexterity, take the trait highlander. You'll rock stealth tests, and as you'll likely be wearing studded leather for the full dex bonus, the trait will cancel out your ACP. So your stealth at Lvl 1 will be +9. That's really good. Also with Cha16 get the trait world traveler so diplomacy is a class skill. It'll get you +8. Having +8 diplomacy and intimidate makes you a great party face as well.
Go pure rager and get lesser beast totem, as the beast totem build means lots of AC at lvl6 and pounce at lvl6.
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You may also consider playing a monk/enlightened paladin with those stats. The paladin doesn't have the paladin code, but is instead all about self perfection.
Monk (1) gives you Wis to AC and flurry of blows. Enlightened Paladin (2) gives you 2 points of Cha to AC, Cha to saves and the ability to beat up one person each day really well.
At lvl3 without any equipment you have AC 20 (jumps up to an easy AC 23 with a bracer of armor, ring of protection and dodge). Your saves will be so high that there will be no reason to cast at you. Start using dragon style for 1.5 strength damage unarmed, and you can flurry for a second attack.
Save up for the gloves which add +1d6 acid damage to your unarmed strikes and an amulet of mighty blows. Laugh as you walk around naked, blocking swords with your chest.
It's a really MAD character. But all of your stats are at legendary levels. So why not make full use of it?
I'll point out that the human option that Grumbaki mentions is a human with the alternate racial trait Dual Talent, which replaces the human talents of their bonus feat, and skilled. In short you lose the one extra feat at 1st level and the extra skill point per level to gain an extra +2 to one ability score. It is an interesting option, I'd probably stick with the basic human for an extra feat, but I'd have to weigh the feat options. This is found in the book, the Advanced Race Guide.
Concerning the characters Dex score, Grumbaki, I'll note he wrote his ability scores in a slightly different order than usual, he has a dex of 16 and Con of 21. With this dex medium armor is probably for the best, eventually taking agile breastplate, or normal breastplate.
About the Grey Walker, you may want to ask the GM how this race is viewed by society, are they relatively accepted or are they heavily persecuted? With some GMs this could be a major factor in deciding on how fun it is to play an uncommon race.
Unbreakable fighter does seem like a good dip for a barbarian, since die hard is a good feat for a barbarian to have. There are several options to choose if you want die hard or increased survivability that won't require dipping:
First is the rage power Raging Vitality, this rage power increases your con bonus while raging and lets you rage while unconscious, this is important since barbarians can die if they are unconscious and their rage ends, since that lowers their con and hit points. Being alive and out is generally safer than being alive and active with negative hp, since enemies will still target you, of course some GMs will target downed PCs if that is logical for the enemies tactic, like a starving wild animal.
Half orcs can take an alternate racial trait that gives them the endurance feat by losing their +2 racial bonus to intimidate, then your only 1 feat away from die hard, I like this option and used it for a barbarian I made, I also had this character take the alternate racial trait sacred tatoo, and the trait fates favored to gain +2 luck bonus to all saves, a very powerful option for half orcs.
Finally unchained barbarians gain temp hp when they rage so they don't need to worry about the hp loss when they go unconscious, although the unchained barbarian is often considered weaker than the regular barbarian, it was intended to be easier to play, so keep that option in mind.
Starting Equipment: save some money for a ranged weapon, a sling and sling bullets is good for a low level high str character, but eventually you'll want a composite longbow with the adaptive magical ability.
Also have money for adventuring gear here is a suggested starting gear for a barbarian (from the book Ultimate Equipment: a backpack, a belt pouch, a blanket, flint and steel, an iron pot, rope, soap, torches (10), trail rations (5 days), and a waterskin. cost 9 gold weight 26 pounds).
You may want to ask the GM about the intended difficulty of the adventure, the last time I played with a GM with a very generous ability score generation method the game was brutally hard, it might not be the case for your game though.
That Gray Walker race with those stats will be OP. The big benefit to Human is the Superstition Rage Power FCB, boosting that benefit to the stratosphere, but with this being a low magic campaign, won't be as useful (though the rage power by itself is still helpful in the events of fighting spellcasters). As has been suggested, Invulnerable Rager will get rid of a lot of mostly unwarranted class features for better overall defenses.
Yes, Power Attack for your first level feat. Following up from that, I'd consider taking the Intimidating Prowess feat, pumping your Intimidate checks for the craziness that is Cornugon Smash (free Intimidate checks for every successful Power Attack you land). Bonus Points if you decide to take the Hurtful feat, giving you an extra Full BAB attack on a successful Intimidate check when an enemy is within melee reach as a Swift Action (you don't get much Swift Action usage as a Barbarian anyway, so this is perfect).
For gear, just grab a Breastplate and a Masterwork Nodachi. You'll want a Mithril Breastplate (with the Armor Expert character trait) for making full use of your Dexterity and nullifying ACP, but that's too expensive starting out, so don't go enhancing your armor until you get that. For ranged options, simply grabbing Amentum (no need to enhance them) to throw at enemies is worthwhile, and doesn't require you to put away or drop your Nodachi to use. With 50 feet range, and being able to apply full strength is certainly more versatile than any Composite Bow that you'll find.
Dipping isn't bad for a Barbarian; it certainly helps the feat conundrum, but you will delay Barbarian progression, and lose out on capstone abilities if you expect to take the PC up to 20th level. It's actually easier for a Fighter to VMC Barbarian, simply because Fighters have the most feats and can spare 5 to not be so crappy.
Thank you for pointing out (again) the house rule for humans.
As for feats: the feat furious Focus is great for early levels, it eliminates the power attack penalty for the first attack with a 2 handed weapon basically.
combat reflexes would be good with a 16 dex, 3 extra attacks of opportunity is really nice. Using a reach weapon would be good if you take this feat a large glaive does 2d8 damage + str and a half with power attack on the AoO could really hurt enemies without reach before they have a chance to hurt your character.
Rage powers: Beast totem is considered one of the strongest since at level 10 you can gain pounce, which lets you full attack after charging. Beast totem gives a nice defense boost too, especially useful in low wealth / magic item campaigns.
With those stats, I'd be tempted to grab one level of Unchained Monk by using the Adopted trait to take the Enlightened Warrior trait (may be a non-lawful Monk). Wisdom that high and free Dodge bonus feat is as good as medium armor, and Unchained Monk Flurry of Blows with a Monk sword (9-ring broadsword or temple sword) on a Raging Barbarian would be a terror. You never need more than one Unchained Monk level, though if you take 3 you can make even more bonus attacks with Ki.