Originally Posted by ThePhanastasio

We say "hella" here, too.

Some other slang that may be unfamiliar that's used:

Nans = Shenanigans. Or, saying you don't believe a statement, thus calling shenanigans.
Example:
Person One - I hear that Mildred Dipplethorpe's baby daddy is Thom Yorke.
Me - NANS!

Firemost: The greatest. The best. Fire is good, and this thing is the most fire. It is super awesome.
Example: Dude, I just ate the firemost brownies this morning!

Mad: Well, this is just used as in crazy. Usually in reference to drug activity, although occasionally used to reference other things as the user sees fit.
Example: I'm sorry I couldn't make the party, man. I was mad tired.

Fo shiz: For real / seriously. Could be a question, or could just mean I'm serious.
Example:
Person 1 - I crashed my car into the college today.
Person 2 - Fo shiz?!
Person 1 - Fo shiz.

Awww, sheee...: Aw, ****. General statement of concern and / or disbelief.
Example:
Person 1 - They're ticketing everyone parked in the side lot, so I hope you're not parked there.
Person 2 - Awww, sheee...