Daniel Loeb of Third Point Capital Management, Yahoo! ( YHOO) is on its fourth - and most highly-regarded chief executive -- in just over a year's time. Talk about channeling your inner Carl Icahn. Were Icahn to retire, it appears Loeb of Third Point Capital would be most suited to keep open an activist investing playbook full of C-Suite fire. At Loeb's prying, Yahoo entered 2012 with a fully-reconstituted board and the company's co-founder Jerry Yang had all but disappeared from the company. Like Icahn, Loeb used the pen to assert much of his power, outlining in multiple screeds why the company's board of directors and management needed to go, while highlighting the value of minority-owned assets abroad. Loeb even played detective in rooting out inconsistencies in former chief executive Scott Thompson's resume, which eventually got the ex-CEO fired. Loeb's penmanship also sketched much hyped deals, such as a proposal to sell most of Yahoo!'s stake in Chinese e-commerge giant Alibaba for $7.1 billion. Now with Marissa Mayer at the helm, there are signs Yahoo! may be on the verge of reinventing itself into a more full-service media company, after it was trounced in internet search by Google ( GOOG). Under Loeb, Third Point Capital has also made savvy bets on the likes of insurer AIG ( AIG), a split of Kraft Foods ( KFT) and Murphy Oil ( MUR), which also looks to headed down a split-off route. If Icahn were to retire, Loeb might very well be the most vocal investor to carry the activist torch. Another firm to watch is the smaller, but fast moving Jeffrey Smith-run Starboard Value, which agitated for a shakeup at AOL in 2012 with mixed results.