I'm sure there is a million of these threads, but figured I'd try my hand.
Primordial Assault - Psy/Dark Dmg - Old gods/C'thulu theme
Tyrannical Melee - Psy/Lethal Dmg - S&M theme (whip attacks)
Amoeba Structure - Absorb and Offensive toggle armor set - Jelly/Amoeba theme that uses offensive toggles to leech protection/health/absorb to itself.
Spear - Leathal Dmg - A proper spear/pike/halberd/trident set (staff gets close but is far from the same theme)
Charisma control - Using your shear charm and good looks to influence enemies.
Praetorian class sets - Two "bad guy" classes in the "Soldiers of Arachnos" theme. ACU, Seer, Enforcer, etc