Taco Bell is a good choice, Bean Burritos with no cheese are tasty.
Chipotle has awesome burritos, rice, black beans, guacamole!!!
Wendy's has baked potatos, unfortunately no vegan margarine. Ketchup will do in a pinch.
I mostly avoid fast food, so that's all I have.
I have always wondered if Taco Bell uses lard in their beans, and have avoided them because of that....do they not?
Chipotle is the only place I go, it's yum! I love a naked burrito with beans, rice, lettuce, lots of really hot salsa, and guacamole. They're huge too.
Unfortunately the company is owned by McDonald's, and I don't really like to support McDonald's with my money.
I do think they were being sold off though, not sure....
Anyways, when in doubt, most fast food places have salads now. It can be hard to find one that doesn't have cheese, egg, or meat on the top, but usually there's at least one option, and then you just have to track down a dressing.
I went to a place for the first time this weekend that seems to be popping up around here called Qdoba. It is like Chipolte (which we don't have out here) AND their guac is non-dairy (a big YAY)! Check it out if there's one near you. I don't know who they're owned by, but it might be another option. They had a few veggie-type options AND the staff was really helpful (at the one I went to, anyway).