English Harbour Casino
Update: English Harbour are no longer taking new players, though the site is still up if you already have an account.
This is the flagship casino of the aptly named English Harbour Group. This casino has been online since 1997 and (at the time of writing) has a 98.18% payout percentage. Caribbean themed, English Harbour being a historic district on the island of Antigua, where this casino is based and licensed.
English Harbour offers 24/7 customer support, and although the payout department only operates during office hours (based on Eastern Standard Time) they are open on Saturday mornings. The casino accepts US players, though some states are banned (Louisiana, Maryland, Oregon & Missouri).