You'll run into tons of shops which are all offering the same thing. 5 or 6 T-shirts for $20. Don't do it. The T-shirts all just wear out after 2 washings and are only good as rags. If you really want to get a shirt, there are plenty of places where you can buy Hawaiian shirts, some cheap, some not so cheap.
Notice that the high-end shops in Waikiki and Ala Moana (Hermes, Gucci, Prada, Chanel, Rolex, YSL etc.) are gorgeous and well-stocked. If you're from Japan or somewhere else where there are ridiculous import tariffs, you'll stock up. Check out Duty Free Shoppers as well -- you'll need a passport. If you're from anywhere else, you can buy all that stuff cheaper at home. Hawaii has a 4.5% tax on top of the ridiculous MSRP. For souvenirs, go to WalMart or the NEX at Pearl Harbor (DoD affiliated.)
Unique Suggestions: Go in to the boutiques and handle all the stuff -- they don't know you're poor and not going to buy. Then you can go home and tell them about the $1,600 wallet you saw (and how the Japanese were buying them like it was the last wallet for sale on the face of the Earth.)
Fun Alternatives: Did you really come to Hawaii to shop? Take a souvenir list to WalMart, buy the Hawaii stuff, then go to the beach, for crying out loud. Or golf. Or poolside. Or something !
The International Market Place has been and always will be a PEOPLE magnet. BEWARE ... 100% vendors in here, out to make a buck. Most of the stuff sold is cheap dime store items, so look for quality to match that high ticket.
Unique Suggestions: Before you go, make sure you know your $limit, or set one. You go without a limit and you will undoubtedly have to buy another suitcase to carry home all your treasures, or ship some home parcel post.
Fun Alternatives: Before you get started anywhere, list down the friends that you MUST buy souvenirs for, carry it with you and this will help keep you from over buying. It also keeps you from being pressured into buying something later that was an afterthought.
BEFORE you do ANY shopping at quaint places, check out WalMart, Longs Drugs, or KMart (to name a few) and check the prices of their souvenirs. These prices will be more appealing to you and your wallet.
Right outside the International Marketplace along the main drag in Waikiki, I ran into a couple of street performers. They are usually there in the early evening, but could be there in the afternoon. Two of the main people I saw was the silver-grey colored robot statue guy. This guy can be very, very boring since all he does is just stand there, but he might move if you give him some money. Another, somewhat more entertaining person to catch is the small man in a pink ballerina outfit. For a little while, he is a funny mime, and uses the crowd for his comedic act and mimics people that walk by and in the crowd. On other nights, I've seen a few others. The cutest thing I saw was a dog with a sunglasses on and a mouse on the top of his head, dollar bills under his paw.
One major pain is doing your best to stay away from all the people walking down the street that give people pamplets of things dealing with religion to attractions and stuff to do. its best to just stay away from them and do your best to walk by them. There are tons of homeless people that walk around, you'll see alot along the beach in the parks. One person I went along with from my group ran into a homeless person walking down the street, having a strong yelling match at every light post the man walked up to. Be careful.