Blade Runner, Black Dahlia, Agatha Christie's Evil Under the Sun, Sherlock Holmes: the Awakened, Cruise for a Corpse (if you are in a retro mood), and about a million more.
And since you like Gabriel Knight, there's a million more to add from a horror genre: Dark Seed 1&2, Sanitarium, Phantasmagoria...
...There's also a nice little game called Insecticide which combines platform-jumping-and-shooting with levels of pure old-time noir detective adventuring.