Diapers.com, Ancestry.com and 1-800-CONTACTS come to mind. Hotels.com, Staples.com, Drugstore.com and Overstock.com may be close. Some like Pets.com obviously didn't work out.
Update: stamps.com and audible.com are also good examples.
See my comment below... branding is about owning a category...you can still make money with a generic name but it will never replace the category name.
I don't care about your comment below, in the one that I replied to you asked, "Can you find one brand using a generic and relevant to the category name dominate a category". I could and I did.
all three of these brands are brandable. I don't think you understand the objective of branding if you think no true scotsman applies here.
Branding is the battle for peoples perceptions, and follows the rules of how our minds perceive things. Your mind is not capable of assigning meaning to a generic term. You can know what they do, but you cant associate it with a category.
"American Airlines" does not mean an American Airline in anybody's mind. Just as Buy.com doesn't mean anything other than a website that might have something to do with the word buy.
Generic domains have all sorts of other value, and you can make lots of money without a good brand. But... Branding is about one thing only... Associating your name as the "Go-To" folks in a category. That association is simply not possible with a generic name.
Update: stamps.com and audible.com are also good examples.