My favorites:
Grim Ward-
Basically, this skill is "I'm going to do something so messed up and scary to the corpse of an enemy that I just killed that even the UNDEAD will be afraid to mess with me". Seriously, how badly do you have to mess up a corpse to get a skeleton to think "Oh no, I better stay away from him, I don't want him to do that to me!". I mean, it's not a spell or a trick or anything- it's just defiling a body and letting the results speak for themselves.
Leap-
Not Leap Attack, just Leap. At high levels, the Barb *NOT ONLY* flies through the air and lands 16 or 20 feet away (take that, Morpheus!), but he lands with such force that enemies the size of small houses who are an entire screen away get knocked back. I mean, these things can stand still when they're getting bombarded by Hurricanes and Meteors and Tornados and yet a Barb hopping up and down can send them flying even if they aren't even in the same room as him. Seriously, people might think that Berserkers are the biggest Barbarian Badasses, but give me a good Double Thrower with lots of Leap and Grim Ward any day. Those skills scream "don't mess with me!" so loudly that even the Minions of Hell listen.
Pierce-
Come on, seriously, how ridiculous is this. The amazon's like "not only am I going to shoot you dead, but I'm also going to nail you so hard that my arrow goes *ALL THE WAY THROUGH YOUR BODY* and continues on to hit your buddy behind you. Oh, and there's a good chance the arrow's also going through again and hitting the guy behind that, and even the guy behind that, too.