The latest 13F season is here, when many money managers issue required reports on their holdings. It can be worthwhile to pay attention, as you might get an investment idea or two by seeing what some major investors have been buying and selling.

Today let's look at investing giant Daniel Loeb, founder of the Third Point LLC hedge fund. Loeb is a well-known activist investor, famous for publicly airing his opinions about companies in which he invests and not mincing words when he's displeased. His activity warrants watching, because the guy seems to know a thing or two about investing. According to the folks at, over the 15 recent years ending in 2013, Loeb racked up a cumulative gain of 961%, compared with just 98% for the S&P 500.

Third Point's latest 13F report shows that it increased or initiated positions in Actavis plc (NYSE:AGN), Cabot Oil & Gas Corporation (NYSE:COG), and Citrix Systems (NASDAQ:CTXS).

Actavis is a $37 billion specialty pharmaceutical giant, up 73% over the past year and averaging 16.8% annual growth over the past two decades. It's buying Forest Labs (UNKNOWN:FRX.DL) in a deal that has some scratching their heads, as Forest Labs is facing patent protection expiration for two key revenue drivers, its Lexapro and Namenda drugs, which tackle depression and Alzheimer's disease, respectively. Still, Forest Labs will provide cash flow, sales strength, and a promising pipeline. Acquisitions are not new to Actavis, which gobbled up Warner Chilcott last year. That helped its first-quarter results, which saw revenue surge 40% year over year and adjusted earnings per share jump 75%. With a forward P/E ratio near 13, the stock seems attractively priced.

Cabot Oil & Gas Corporation has been posting strong, and accelerating, revenue and earnings growth (averaging in the double digits over the past three years), and with a forward P/E ratio near 23 its stock seems attractively valued. Its first quarter featured average production jumping 34% year-over-year, while costs per unit dropped 19%. Cabot is focused on natural gas, and, while enjoying great performance from its Marcellus assets, it's spending more on its Eagle Ford shale development in a shift that could pay off well over the long run. Production has been growing in the Eagle Ford, while Marcellus pricing has been weak lately, so the shift has many nodding in approval.

Cloud-computing and virtualization specialist Citrix Systems is a $10 billion business that has been in a bit of a slump in recent years. It posted a fairly solid first quarter in April, with revenue jumping 12% year over year and earnings topping expectations, but then management lowered near-term projections. Its profit margins and bottom line have been shrinking in recent years, but free cash flow has been growing, and there's no debt concern with Citrix. The company is developing apps for Chromebook and trying to adapt to the growing importance of the mobile realm, but it faces tough competition and isn't yet firing on all cylinders. Management recently upped its share repurchase plan, too, which can boost shareholder returns.