Mark Pellegrino is best known as Jacob from Lost and Lucifer on Supernatural.
You can see Pellegrino in many other shows also. He has mad appearances on Northern Exposure, ER, Without a Trace, The X-Files, NYPD Blue, CSI: Crime Scene Investigation, Knight Rider, and The Mentalist. He has also had a recurring role as Paul on Dexter.
You can currently see Mark in Syfy's Being Human.