A brand not yet mentioned is WE. If you are fond of something with the approximate "footprint" of a ZT 0900, then take a look at the WE 605F. It sports a 3.0" flipper blade of the same S35VN steel as the ZT and is very, very close to the same blade thickness. While the 605F is obviously intended as a flipper, the sculpted drop point blade features a nicely formed, almost aerodynamic-seeming opening hole. The unassisted flipper action is extremely crisp like all the WE knives I've personally handled. (I do own a few Kizers, and even thought well enough of the Kizer Nomad to buy two of them, but to be brutally honest, most Kizer flippers are pretty lazy in deployment, very reminiscent of the well known ZT 0560/0561 Hinderer.) And because the 605F is not spring assisted, if you choose to use two fingers to "pinch" the blade open, there is no spring tension to overcome; it's a pretty easy opener if handled this way.
Now for a few points that may or may not be of import to you. First, the WE 605F is going to set you back roughly 90 bucks more than a ZT 0900, however, for the money you will be getting quite a bit more fine machine work as well as more choices in handle and blade color combinations. Second, it's a product of the People's Republic of China which admittedly can be a deal breaker for some folks who are of a certain mind or who have yet to inspect a well crafted Reate or Rike knife. Third, WE designs tend to be quite expressive of certain design elements and tend to be dismissed by buyers who appreciate a more restrained or conservative appearance. Fourth and last, WE employs a proprietary fastener, maybe best described as a "reverse torx." My WE knives all came with an appropriate adjustment tool, but it's I think fair to point out that you are unlikely to find a proper tool at your generic big box home improvement emporium.
Obviously, I find the 605F to be quite impressive. Try looking one up. My purple example with a two-tone black and silver blade has seldom failed to generate a favorable comment.