The last time that I visited Oahu, I drank beer from Kona Brewing Company. I tried the Longboard Lager, Big Wave Golden Ale, Firerock Pale Ale, Lavaman Red, and one of the porters, but I can't remember which one. All of the beers were very good, but I remember the Lavaman Red being my favorite.
I mostly drank bottles, but my wife and I did visit the brewpub at the Koko Marina in Honolulu as well.
Hope that helps,