I thought it might be interesting to get a, say, multicultural viewpoint. One of the highpoints of living in a different country is learning all of the ridiculous, hilarious, and flat out overused words and expressions.

Krass: (adj.) Cool, sick, sweet, etc.

Stumpf: (adj.) Literally translated, blunt. Said in reply to a dumb comment.

Halt die Fresse”: Shut your face.

Zicke: (n.) Short for “Ziege”, or goat. Equivalant to the Englisch “Bitch.”

...chen: (adj.) Little. Can be put at the end of any word to make it seem smaller. Exp. Kätzchen (Kitty) Brötchen (Little Bread) etc.

I hope this provides a decent insight into the wonderful world of German teenage culture.