Second votes for: House, Dexter.
They both feature very unique characters – but both require you watch it from the beginning to really get all the inside thoughts and jokes. Not watching them from the beginning will put you big time in the guessing dept – and you simply won’t understand the characters or enjoy them as much.
The first is about a radical doctor going through his issues while pursuing the purest distillation of truth possible.
The latter is about a serial killer killing serial killers – based on an amazing book series (which is also a ton of fun to read.)
Other shows or recent interest: Lie to Me – based on a real life psychologist and researcher, although with a part of fiction added to it (not to the techniques though).
An older show but a huge favorite: Life with Damian Lewis (same guy from Bands of Brothers). Only two seasons to catch up, cop who did time for multiple murders but then exonerated.
Comedies – I’m a big fan of Extras and The Office (UK) by RIcky Gervais – both of which are two seasons and not that many episodes. But hilarious nonetheless. Also, A bit of fry and Laurie – which is a blast from the past, but you can see the character from House in his previous achievements with Seven Fry – and Hugh Laurie (House).
The Philanthropist is another favorite, features stories made into fiction inspired by a real philanthropist.
HBO shows are usually amazing – a couple of absolute favorites: Six Feet Under and In Treatment – the first deals with loss, latter with therapy.