Westie: One who dwells in West Auckland. More commonly associated with being a bogan, or Outrageous Fortunes. These people can mostly be found in suburbs such as Massey, Glen Eden, Henderson, Ranui, and Sunnyvale. I grew up in West Auckland, but am not a 'Westie'.
'Hard out' or 'hard': When in agreement with a colleague, you may reply by saying 'hard' or 'hard out'. There is usually some emphasis put on 'hard', e.g. 'haaarrrrd'. I sometimes say this because I think it's funny, hard out funny aye.
Mean: Usually pronounced 'meeeeeean' and more often than not, is followed by 'bro'. Similar to 'hard out' in that one would use this word after hearing a statement they are in agreement with, or which gives them some pleasure.
Choice: A typically kiwi word, I think. Similar to 'mean'. When you think something is 'choice', I imagine you would quite like the thing in question, be it an object, an act or an idea. E.g. "I think your dress is choice bro." (Bro is optional).
Chur: Similar to mean or choice. Used when you think something is 'choice' or as an alternative to 'thank you'. E.g, When you're chilling with your bros, and one of your bros makes you some toast, you can say 'chur' or 'chuuuuuurrrr'.
I reckon: I don't know if this is a typically kiwi thing to say but I hear people (kiwis) saying it a lot and with gusto. For e.g. when you agree with something one of your bros says, you'd be like 'I reeeecken'.
Sweet as: 'Sweet' or 'sweet as' is similar to most of these other words. It is used to confirm that something is okay, or to communicate that something is good. E.g. "I'm going to be a bit late" "Sweet as". Also, adding 'as' to things is kiwi as.