my favorite is Stick, just because it was so over-the-top "vintage" that it borderlined cheesiness, but in a tongue-in-cheek, fun kinda way. Kill Shot was probably his most tense one. Bandits were pretty good too.
Haha I read so much Leonard when I was younger (in high school) but after a while you realize they're all the same. His cowboy stuff were pretty good too. He's like a Hemingway without substance. Even got his anti-Cuban-and-black people streaks every once a while, but nothing too overt, except for the fact that his heroes are always white and his villains are very often not white...
He's the one guy that you can catch up just by watching the movie adaptations, they've been fairly accurate so far.