I think a lot of the lists are different because different people have had different experiences.
For instance, I've noticed on here that a lot of people feed their rabbits cabbage and broccoli, both of which are complete no-nos in my mind. They cause gas (or can, I guess), which leads to bloat and death. I also won't feed my rabbits potatoes or tomatoes (tomatoes are actually part of the nightshade family). But, I've never had problems giving my rabbits my apple cores (and I've seen a few lists that say no apple seeds).
The best thing to do, is to take a basic list, and work from it. If your rabbit shows any problems the week you introduce a new vegetable (I've never found a fruit that was bad except in too large quantity), put that vegetable on your bad list
Some vegetables that I haven't seen on any bad lists are carrots (including tops), beets (including tops), celery, spinach (in small quanitities), and dandelions.
Absolute no-nos are tomato greens, milkweed, flowers from bulbs, and legumes (beans, etc.). I usually add to the "no" list anything that you're not absolutely sure is safe.
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