The best ones are the premium WordPress themes, but not all are equal.I have Thesis which is my absolute favorite! This is on Tips4pc and Letsbuildwebsites.What to look for when choosing a theme:1) Back-end Support in Premium ThemesWhen something goes wrong or you want to adjust something you need help... Not good to waste your precious time figuring out what the pros can fix in seconds. 2) Support for SEOSEO should be inbuilt to your theme now days. 3) Future UpgradesYou want to buy a theme that is popular and updated regular. Do not buy a theme where the developer is going to disappear one day. 3) Customizable A good theme has settings you can change in the dashboard without touching the code of the theme. Thesis has amazing options! 5) Price OptionsThe price can be a deciding factor. For example you do not want to be charged a recurring fee.. I like to pay for a theme and get continuing support and updates.