UPDATED x2 21 Dec 2010 with another big one.
UPDATED 10 Dec 2010 - a hat tip to the commenters for remembering some I forgot!
So what if the Korean language is not your first language? You can still use it in a way that's probably not used by the locals. These are the examples I've heard - or used - of recent:
chunner: referring to a 1,000 (cheon) won bill.
Do you have a chunner?
Give me a chunner and I'll buy you a Coke.
manner: referring to a 10,000 (man) won bill. Pronounced 'mahn-ner'.
Give me a manner and we'll call it even.