Hercules Poirot, Agatha Christie, and David Suchet
I am a fan of Agatha Christie http://www.agathachristie.com/, and especially her detective Hercules Poirot http://en.wikipedia.org/wiki/Hercule_Poirot; http://en.wikipedia.org/wiki/Hercule_Poirot. Although other actors have played Hercules Poirot, I most identify him with the portrayal by David Suchet http://www.famous-pages.com/david-suchet/. Those are great shows.
I also enjoy the Miss Marple shows, but not as much as the Hercules Poirot shows.