Honestly the only ones I DO like are lockout, ascension and beaver creek. Not quite in the same level but still decent enough are Ivory Tower and Colossus.
Midship: Too small and repetetive grounds.
Burial mounds: By far my least fav. It's huge, its hard to get a decent gun, it looks like shit, completely asymetric. It's just garbage. Oh and I also hate that sound that it makes. It sounds like a rusty gate swinging.
Zanzibar/Headlong: both sort of the same deal. Too asymetric and theres too much shit lying around them. They went for a realism type theme with these and I do not like it.
Coagulation: I loved old blood gulch but have yet to have fun with coagulation. I think part of that is the games live makes me play like assault and ctf. Not fun. Halo 1 ctf was good, they killed it here.
Waterworks: Enormous, dark, annoying shaking thing. Bleh.
Come to think of it, most of the maps I like run games like slayer, odball and KoTH. I used to love CTF but they ruined it in halo 2 so that is probably a big part of why I don't enjoy the bigger outdoor maps.