I would wear a huge, full-head mask from a mascot outfit. Or a big papier-mâché thing with a dopey face on it. I would drive to the kill area, steal a motorcycle a few blocks from my car (somewhere without cameras), then ride to the target wearing my ridiculous headgear. Gun down some rich pharm exec, lose anyone tailing me, get back to my car and drive home.

Papier-mâché would probably be best for the headgear. I could toss it somewhere on my way back to my car then make a new one for the next kill. Other than that I would wear really non-descript black clothes and black shoes. Black to minimize visible detail, so that if I have to ditch the motorcycle and papier-mâché I can walk on foot like a normal pedestrian even as cop cars whizz past me.