Wow! Thanks guys for all the great responses. I should mention I'm a Kiwi from the dim and distant past, but have been living an expat life for far too long. I have been to Auckland before, but never really done much touristy things, mostly visited relatives. One the trouble is most gaming shops seem to disappear/move between visits. Living in Europe, its kind of expensive to get back "home", and with kids and a mortage, it seems to take forever to save the cash to go.
The reason for my trip is twofold: a dear friend is getting married in Samoa, so I had to go to the antipodes anyway, and my mother's celebrating one of those decennial birthdays, so I want to treat her with some outings. Then by pure happenstance, an old boarding school buddy got in touch, so I'll be visiting him as well.
I really like the area around the War Memorial. Strange as it may sound, I have lots of nice memories from around there, and I think it is a fantastic museum. I do try and visit it every time I go to NZ.
Piha is also a favourite, I might try to get out there again this time, altho' as you guys say, it isn't really the best time of year.
MOTAT sounds great, and I have a dim recollection of having been there as a wee laddie with my father. That was a very long time ago. Don't think my old mum is too into vehicles. If I had more time, I'd definitely visit it.
Devonport, I think warrants further investigation, as does Rangitoto. Sort of semi-amateur photographer, I think I'll enjoy scrambling around Auckland's future doom. I'll definitely be paying King of Cards (I'm a MtG nut) and Vagabond a visit, so those were great tips.