4. Special Agent Frank Lundy - Season 2
Special Agent Frank Lundy is brought to Miami to investigate the Bay Harbor Butcher case, when the bodies Dexter has been dropping into the ocean are found by divers. He is famous for his ability to break seemingly impossible, high-profile cases, often coming in and discovering crucial evidence that the local police department overlooked. Lundy comes dangerously close to discovering that Dexter is the Butcher. So close, in fact, that Dexter has to frame Sgt. Doakes in order to keep from getting caught. Lundy has an interesting, unorthodox personality that makes him incredibly interesting to watch, such as his enjoyment of the "little things" in life, like his cucumber cream cheese sandwiches, every day at 1 o'clock. His romantic relationship with Deb has had tremendous lasting effects on her character throughout the show, and I would argue that Dexter learned more by trying to outsmart Lundy than he's learned from his various victims.
Memorable Moment: Taking one look at a fake letter Dexter wrote hoping to throw them off his trail, and deciding that the Butcher must be someone who works in law enforcement. Excellent police work, Lundy!