5. Agent 47
Whether putting together cold and calculated plots to take out his target or running in guns blazing to empty a room (up to the player, of course), Agent 47 is the original contract killer who makes his own rules. His trusty silverballers backing him up, an endless stream of supplies to quell his victims, and the quintessential "quiet and scary" guy persona make him one of the suavest assassin's we've ever seen, even when he's piddling around in an ice cream van or climbing in and out of dumpsters. Still awesome.