Sorry my mistake Oahu please.
Well, it depends on what you are looking for. If you like old school Midwestern/cracker type crust, there is a Shakey's on Oahu in Waipau at the Waipahu Shopping Center strip mall but you would have to drive from Waikiki: 94-60 Farrington Hwy, Waipahu.
In the same style there is also Round Table Pizza with at least 2 Waikiki locations: one at the Hilton Hawaiian Village and the other location is at the other end of Waikiki, at the Ohana East Hotel: 150 Kaiulani Ave, Honolulu, HI. It is a nice sports bar, but I am seeing on the internet this location may have moved or be closed.
Other styles of pizza that are more mom & pop that are worth checking out are:
Happy Valley Pizza and Pasta over by Diamond Head.
Amina Pizza on Kalakaua Ave
Rosarina Pizza on King Street