My favourite races are the Vulcans and the Ferengi.The Ferengi because of their lust for latinum. And the Vulcans because of their logic.
Well obviously the Humans; but if i was to go for an alien race, it would have to be the Romulans because... a. There ships are very powerful - especially the D'Deridex Warbird b. They are silent but deadly, i.e using the cloaking devices c. They're so arrogant ;) d. They always seem to know whats going on - probably due to the Tal Shiar