Dashiell Hammett. Anything, really, not just The Maltese Falcon.
Elmore Leonard. Pretty much everything.
And, of course, Ross Thomas. Especially the ones with Cyril "Mac" McCorkle & Michael Padillo / Artie Wu & Quincy Durant in them. Yes, rather thrillers, but crime is crime.
Gisbert Haefs. Solid conventional crime novels, thrillers, crime/spy novels set in historical settings, a bit of SF, some weird stuff and some outstanding translations.
Gert Prokop. Did a couple of books that are both solid crime stories and SF at the same time, set in a dystopian America, with the added bonus of reality catching up with fiction dreamt up 30 years ago just a little bit more each year.