Wal Mart, Oahu
Don't get ripped off. If you can buy it on the island - you can buy it at Wal-Mart. I shopped in Mililani and it was wonderful. "Locals" flip-flops were $3.67. Macademia nuts are $1.80 in a gift box. Beach towels are $7.50. Get your goods here and save a few bucks.
What to buy: Tiki Gods, beach towels, lei's, bottle openers, coffee mugs, flip-flops, macademia nuts, coffee, aloha wear, and all of your other island needs. Buy inexpensive snorkeling sets here for $10-$20, instead of paying rental fees. Ladies, try the kid section - basic set is $10 and fit me better than the adult set.
What to pay: Cheaper than you can buy it anywhere else on the island. And it's the same stuff.