Any of the Sackett books
Sitka
Hondo
Bendigo Shafter
Mustang Man
The Broken Gun
Absolutely awesome writing!!!
Bendigo Shafter has always been one of my favorite L’Amour book hands down. But any of the Sackett books are good. His private detective stories are good as well.
One book I wanted to read but never have is The Walking Drum. I think it was his last big book before his death.