Dude
Fascinating article here about the origin and uses of the word "dude". Here are some meanings:

An admitted dude-user during his college years, Scott Kiesling said the four-letter word has many uses: in greetings ("What's up, dude?"); as an exclamation ("Whoa, Dude!"); commiseration ("Dude, I'm so sorry."); to one-up someone ("That's so lame, dude."); as well as agreement, surprise and disgust ("Dude.").

I like that "agreement, surprise and disgust" bit. When I read that I was like "dude".