My stealth rogue standing beside a gigantic ogre.  Followed a few seconds later by my rogue standing beside a gigantic dead ogre.  Seriously, playing a rogue is the closest you can come to one-shotting a mob of equal level.

PvP.  Now the rogue is the only toon I PvP on.  Personally, I’m not a fan of PvP, but on my gnome rogue, it feels like he was born for it.  I absolutely love the panic I can imagine in my victims as my little bundle of death stun locks them and whittles them away to nothing with his little blades of fury.