I want to be using a pistol mostly, and wearing some form of suit a lot of the time.
Woops, New Vegas :p
NCR Ranger Combat Armour, and either Maria or the .44 Magnum Revolver. Wear a cool hat, I guess?
Lucky shades from legion safehouse, benny's suit, vance's lucky hat and mysterious magnum.
assains suit from dead money is nice for light armor and has plus 10 to sneak. pistols such as maria, weathered 10mm, lucky, mysterious magnum and that gun work the best. first recon beret is a must its probably the best head piece in the game and easy to get, lucky shades are good if your legion liked.