I think everyone's covered all the veggie options out there.
Our bunnies get a constant variety. In order to keep things fresh, we go through phases. I'll buy arugula, romaine, & parsley...then on the next shopping trip it'll be radicchio, butter lettuce, & dill...then another variety...
I try to buy 3 different base greens and rotate them to make constantly different mixes. I add a few bits of other veggies to the salad along with a small piece of fruit. My bunnies enjoy broccoli, cauliflower, baby carrots, green peppers, red peppers, and the occasional bit of celery. Fruits of choice for them are: blueberries, strawberries, & apples (their 3 favorites). They also eat cherry tomatoes, melons, pineapple, & grapes...but with a bit less enthusiasm.
Cucumbers and zucchini are absolutely rejected in our household.
From the yard/garden I harvest dandelion, lemon balm, mint, beet tops, & radish tops. I've noticed that the wild cottontails in the yard enjoy the flowers from our violets and clover leaves...but I've not researched that enough to know if it's really a good options for our bunnies.
Our rabbits get unlimited timothy hay (with an occasional other hay variety about small bag per month), timothy based pellets in the morning, and a large fresh salad at suppertime.