NEW YORK (Reuters) - Two of the most prominent investors in the world, Carl Icahn and Bill Ackman, had Wall Street mesmerized on Friday as years of acrimony exploded into a bruising verbal scrap on live TV. Initially CNBC was only talking to Ackman, but then the cable TV station put Icahn on as well and all hell broke loose. The argument centered on nutritional supplements company Herbalife Ltd , in which Ackman has had a well-publicized short position that Icahn has slammed. ...