4. Doctor Salvador (Resident Evil 4)
Who can forget the first time they heard a chainsaw revving up as they tried to take on the crazed villagers in Resident Evil 4? It's a noise that anyone who's played the game will associate with one of the game's fiercest enemies, the so-called Doctor Salvador (though we find his medical credentials rather dubious), a chainsaw-wielding, burlap sack-wearing maniac who will make no pains about separating your head from your body if you hesitate for more than a nanosecond. Taking the big boy down is far from easy, as handguns do practically nothing against him. The best line of offense is either using grenades to slow him down, or blast him off his feet with a shotgun and then just keep wailing away until he's no more. More terrifying than the vast majority of the game's bosses, few enemies in the video game world raise my blood pressure as high with one mere sound.