Can't believe no ones mentioned it, but the sound of someone going hostile against you in Diablo 2. From playing on hardcore that sound makes my heart jump. For anyone who doesn't know how hardcore on D2 works, if someone kills you, you're character stays dead and you loose any progress you made with them. So you have to make a new character, relevel, beat mission all over again and try to get good gear again. That sound basically means someone is on their way to come murder a character you've put hours into.