If you forget to pack a converter, you'll find a selection at duty-free shops in Auckland's airport and at electrical shops in towns and cities. The electrical current in New Zealand is 240 volts, 50 cycles alternating current (AC); wall outlets take slanted three-prong plugs (but not the U.K. three-prong) and plugs with two flat prongs set at a "V" angle.
Consider making a small investment in a universal adapter, which has several types of plugs in one lightweight, compact unit. Most laptops and mobile phone chargers are dual voltage (i.e., they operate equally well on 110 and 220 volts), requiring only an adapter. These days the same is true of small appliances such as hair dryers. Always check labels and manufacturer instructions to be sure. Don't use 110-volt outlets marked "for shavers only" for high-wattage appliances such as hair dryers.
Steve Kropla's Help for World Travelers has information on electrical and telephone plugs around the world. Walkabout Travel Gear has a good coverage of electricity under "adapters."
Steve Kropla's Help for World Travelers (www.kropla.com.)
Walkabout Travel Gear (www.walkabouttravelgear.com.)