Biotech and pharmaceutical stocks made some of the biggest headlines this year, as 2015 saw massive waves of M&A activity, including the Pfizer (NYSE:PFE) and Allergan (NYSE:AGN) merger, the second-largest deal of all time valued at $160 billion. Other companies found themselves in the spotlight for less than desirable reasons, such as Valeant Pharmaceuticals (NYSE:VRX), whose stock has tanked in the past several months.