What makes you enjoy a Protagonist?
Personally liking a protagonist does not appear to be a necessary condition for enjoying the protagonist. So to be clear I am asking you to articulate why you have particularly enjoyed certain protagonists and why others have fallen flat, or failed to appeal.
Some of my favorite protagonists are Tyrion and Jamie Lannister from ASoIaF, Rupert Avery from Feist's Serpent War, Matt Cauthron from TWOT, and - though it pains me to admit it - Richard from the first two SOT novels. I am sure this is not an exhaustive list and I'll kick myself for not recalling some later, but off the top of my head...
Attempting to analyze why I enjoy these characters so much is difficult, but most of them appear to have an odd combination of self confidence and doubt and a dark sense of humor - with the exception of Richard.
Since I am currently attempting to shape my own protagonist, and thus have been giving this some considerable thought, I would appreciate hearing your opinions. I am also very curious as to which protagonists people have most enjoyed.