This is a hard one. I don't have a whole lot of experience with a lot of different breeds so I have to go off a lot of hearsay and good looks!
Absolute favs:
Fjords - I've worked with two of them. Cuddly, big-hearted little guys with 'hawks to die for. teehee. Intelligent as all get out. Stout and calm. I'd love one, one of these days.
Mustangs - enough said. I love the Spanish lines, with the big ole roman noses and big bones. We see them a lot out here, and the captured ones generally make terrific, trustworthy mounts once gentled. Not that I am advocating the BLM's steady emptying of our lands of every flipping wild horse...grr.
Belgians - I'm a sucker for drafts, but I've been around Belgians the most and I have to say, there's just something about them that I really like.
I also <3 Cleveland bays, morgans, clydesdales, *any* of the warmbloods really.
I'm terrible with these things...never can choose just one.