I'm not sure if this is the right place to post this, but I can't find any recent relevant thread.
To begin with, I don't like the idea of over - benting the rules. I mean, taking a flying familiar and having a lot of weight and then casting benign transposition to fall on the enemy for weight damage... well, I don't feel like it, except if you are in a munchkin - like game.
So in my effort to control the Frenzied Berserker, without having to bent the rules (like with Iron Heart Surge or Righteous Wrath) here follows my build:
Race: 1/2 Orc (I choose 1/2 orc for two reasons. First, the flavor. Second, the feat Channeled Rage (RacDes))
1st lvl Barbarian 1 ---- Totem:Lion (CoCh) Pounce instead of fast movement, Rage 1/day
Flaw: Shaky (-2 ranged attack)
Flaw: Murky Eyed (roll twice vs concealed foes, if one is a fail, you fail to hit) --- both flaws from Unearthed Arcana
Feats: Power Attack, Extra Rage, Channeled Rage (the extra feats due to flaws)
2nd lvl Fighter 1 ------ Feat: Cleave (bonus)
3rd lvl Fighter 2 ------ Feats: Intimidating Rage, Improved Bull Rush (bonus)
4th lvl Fighter 3 ------ (+1 CON)
Notes: The fighter levels are obviously for the bonus feats. The feats Channeled Rage and Extra Rage are for later control of the Frenzy. The 3rd lvl in fighter seems useless, but it is required for the 4th llv fighter which gives a bonus feat. The +1 CON could be assigned to STR instead, but since the character is going to lose a lot of AC to hit more effectively, he is going to need that extra Hps.
5th lvl Fighter 4 ------- Feat: Leap Attack (bonus)
Note: By this lvl the character should have no problem maxing Jump and Intimidate skills. They are the only prereq. skills. The few remaining skill points may be assigned as seen fit (perhaps some Jump - boosting skill tricks from CoSc).
6th lvl Barbarian 2 ------- 1/2 Orc alternate barbarian (RacDes) Reckless Charge
Feat: Shock Trooper
Note: I choose 1/2 orc alternate feature (Reckless Charge) to get +4 when charging without having to pay a feat for it (Furious Charge). I personally dislike Headlong Rush because you provoke AoO from EVERYONE in your path.
7th lvl Outcast Champion 1 ----- Aura of Confidence (add class lvls of Out.Ch. as bonus to Will saves, even to allies up to 30', always active!)
8th lvl Outcast Champion 2 ----- Avenging Strike (deal extra (d6 X class lvls) dmg to a foe that hurt an ally, CHA modifier times/day)
9th lvl Outcast Champion 3 ----- Desperate Fury (get +2 STR, CON, DEX when fatigued or exhausted, ends if frightened, panicked or cowering)
Feat: Destructive Rage (useless, just prereq. for Frenzied Berserker)
Notes: The Outcast Champion is an excellent PrC. You get your class lvls as bonus to Will saves (and often so do your allies). You punish those who dare hurt your party. You boost up just when you need it the most, possibly when rage and frenzy ends. You only need 3 lvls in it though, since the abilities confered at the 2 remaining levels are just not worth it. And of course, you need the bonus to Will to count, so you need at least a +3.
10th lvl Frenzied Berserker 1 ------- NOW we're talking! All the way Frenzied from this point on!
Now, with a decent WIS score (13 to 15) you get a +1 or +2 modifier.
Being barbaric - 10th lvl you have a base Will save +2.
Supposing you are already in Rage, when you decide to Frenzy you have another +2.
Your STR (enraged + frenzied), supposing an initial score of 18, is 28 which gives a +9 modifier. You can add this as an immediate action by spending 1 daily use of Rage (hence the Extra Rage feat) to one Will save.
Your Outcast Champion class lvl gives a +3 modifier.
So, the modifier to Will save to end the Frenzy voluntarily (DC20) is:
+2 (base) + 1 (or 2) (WIS) + 9 (STR) + 2 (rage) + 3 (Aura of Confidence) = +17 or +18 In other words, you fail only on a 1 or 2.
I suppose it won't be so difficult to make it, will be? Even with a mediocre WIS (10 or 11) you get a +16.
Final notes: I suppose a riskier player could omit the Shock Trooper routine, so that leaves two open positions for feats (since Improved Bull Rush by itself is not so necessary). Of course, this is a non - magic item build (valorous weapon and magical protection would make a difference here), without too many "exotic" additions (dragonborn, other templates, warforged etc) and without class deviations (levels in casting classes). With 12 + CON x lvl + 2d12 + 7d10 Hps and Diehard from Fr. Berserker 1 he has a good chance to remain conscious long enough to drop at least the bulkiest foes. For those who would protest about investing 2 feats to control the frenzy (Extra Rage, Channeled Rage) the reply is simple. Who doesn't need an extra rage and what fighter - type character has ever found useless a major boost to Will saves? Finally, I do not forget to pinpoint a significant drawback, regarding xp penalty from 7th lvl and on.
But then again, nobody's perfect. Especially an outcast pissed off 1/2 orc...