Ibram Gaunt, Colm Corbec and pretty much the entire Tanith First and only (Gaunt's Ghosts), with the exception of Rawne (who is a psycho), Larkin (who's mad), Feygor (who's generally just unlikeable), and Milo (who is filthy psyker-spawn, and unnerving). *
Everyone else, however, is a cardboard cutout, or a complete and utter asshat, despite this traditionally being the role of Commissars in the 41st Millennium (Gaunt only shoots 2 people in the first three books, and all of these are officers. Wha?).
*Let me explain this. The First and Only are, in the fluff, a brand new regiment mustered from a world with about as much military tradition as Switzerland. Abnett explains how they make excellent scouts, by the fact Tanith is a forest world where the trees move. What he fails to explain is how the Ghosts are somehow experts at moving stealthily through swamps, cities, warzones, trench systems, are all crack shots who would put a Cadian to shame, and masters of knife fighting. Yes, he writes a bloody good book, but he in essence creates a super-regiment out of what should be a bunch of terrified militiamen. Gaunt is something else. Most of them (Caffran, Gaunt, Corbec and a few others) are really, really great guys, and, for that reason, I found myself admiring Major Rawne for his crazy and style.