Wahiawa has your basic grocery stores, drug stores, car parts stores etc. For the really big shopping, you will probably have more luck in Mililani which is no more than 13 minutes down the road, on Kamehameha Highway.
What to buy: There you will find WalMart, and the Mililani Theatres, amongst other smaller shops that cater to your needs. There are tons of fast food shops here also. No tourist stores, so prices are more suitable to the budget than, say, Waikiki.
What to pay: Average.
Open-air shopping center in the heart of Waikiki. It has a waterfall under a big tree. They have a Food Court with local and international food. Also they Hawaiian entertainment five nights a week. Open daily from 10:00 a.m. to 10:30 p.m.
What to buy: Souveniers, etc
What to pay: as much as you want
Vendors of Hawaii selling anything and everything for tourist.
This was on the way to the Pineapple train ride booth.