For ranking - .org, .com, .net, .info
For selling - .com, .org, .net, .info
But at the end of the day if the content is good and you throw enough backlinks at it then you can rank anything.
But if all things are same i.e. content, links, onpage SEO, etc. then for search .org is the best... but if you plan to sell the site then always go for a .com, it will be easier to sell and also earn more.