Halozyme Therapeutics, Inc. (HALO)

Large biologic drugs have to be infused intravenously over hours in a clinic. The company's enzyme temporarily loosens subcutaneous tissue, and the same drug is given as an injection in minutes. For the patient that is the difference between a hospital trip and an injection at home; for the manufacturer it is a way to extend a brand's life.

The company sells nothing itself: it licenses the technology to pharmaceutical giants and takes a share of their sales. Costs are minimal, so profitability is exceptionally high. Risks: expiry of the patents on the technology itself, dependence on a few partner drugs and litigation. The company pays no dividend but buys back stock actively.