Quantum Berserker (Lv14)Venerable Half-orc, Half-orc ParagonUA 2/Barbarian (Berserker StrengthPHB2) 1/Sorcerer 4/Dread WitchHoH 4/Nightmare SpinnerCM 3
Feats: 1: Endurance, 3: Intimidating RageCW, 6: Ettercap BerserkerUE, 9: Diehard, 12: Practiced Spellcaster (sorcerer)
Spells: Cause Fear, Scare, one mind-affecting illusion
Berserker Strength is a barbarian ACF from PHB2. Instead of rage, they gain bonuses when their HP is below (5 x barbarian level). While not typically very useful, it's notable in that it doesn't require an action, has no limit on daily uses, and "any effect that would normally apply only during your rage applies whenever your berserker strength is active". It doesn't count as rage for prereqs, but that's easily solved by picking up rage from another source (half-orc paragon being the most accessible).
Ettercap Berserker is a feat from Unapproachable East which grants you a +6 bonus to Constitution while raging. This has an unusual interaction with Berserker Strength - the extra Con increases your hit points above the 5x level threshold, thereby causing it to turn off. But as soon as it turns off, your hit points drop and cause Berserker Strength to turn on again. You've created an infinite loop.
But what can we do with this? The Intimidating Rage feat lets you pick an opponent whenever you enter rage, and make an Intimidate check to demoralize them for as long as your rage lasts (though you can only affect one opponent per encounter). Nightmare Spinner's Spirit Chill class feature inflicts 1d6 points of nonlethal damage whenever you render an opponent shaken. You are now dealing an infinite amount of nonlethal damage to anything that's not immune to fear.
Dread Witch adds some extra utility with its Delay Fear class feature, which lets you delay the onset of fear effects by up to (Cha modifier) minutes. Imperious Command
DotU could also be useful, allowing you to potentially stun-lock enemies even if they're immune to nonlethal damage.