Pretty much anything from the DRK skillset. Even the standard Power Slash rotation just looks cool with every sword swipe having this cool red streak when the sword is swung.
Abyssal Drain just looks and feels so bad ass when used on a group of 4- or more enemies.
Delirium literally has your character generating dark aether, forming it into a ball and absorbing it to restore mana.
I'm a bit biased though...I literally bought HW because DRK was my favorite job. I love everything about this job even if it isn't in the best spot right now.
