The tuxedo/dinner jacket. Whatever you want to call it, a formal evening jacket is the quickest way to slick, as long as you nail the fit.
(Daniel Craig as James Bond)
Tuxes were named after an American socialite in the 1800s. Traditionally they were black or dark blue, with grosgrain or satin lapels, but these days, anything goes really, patterned, brocade, velvet, pastel - just make it sharp. And adding a bowtie? Your call.