I have a couple of dozen-ish ZT knives and my most carried models by far are 0770cf (M4 and regular versions), occasionally a 0450cfzdp and last but not least the 0454. The 0770cf knives are the best mix of "carries well cuts well" functionality of the bunch, to my way of thinking at least. They benefit from thinner blades that don't follow the ZT herpaderp tradition of having the thickest part of the blade run right through the middle of it, top to bottom wise (which makes most of them super fat behind the edge), and light enough to be very pocket friendly.
I really like some of the fat, log-splitter wedge-ey models, though, like the 0801, 0456 and 0630. Even if they're not spectacularly good cutting tools, I enjoy them being in my life so they get carried some.
If I had to pick one overall favorite, it would have to be this one because she's purdy (baby photo taken on my kitchen counter):
The copper brazing lines have long since tarnished, she has some scratches and she's been sharpened, of course, but she's still a looker, IMO (photo from the last week, in not particularly flattering lighting):