My girl LOVES her Arugula!! If I've made a salad and added that in, and she can still smell it on my hands, she'll run around the room and thump at me until I give hers some!!!
I call it her "bunny crack," cause the minute she has it she gets insanely happy, and will be extremely insistent until I give her some!! (Trader Joes is the one she likes the best, but because its the freshest, and it stays good for longer than any other store's).
Otherwise she loves broccoli, romaine lettuce, broccoli, baby spinach, cilantro, carrot tops (which I put through the top bars of her cage over night to give her some entertainment) and the carrot itself.
Thats all I've tried her with, but she's liked pretty much everything I've offered so far!! (Our vet gave me a list.)
But fair warning, I think the broccoli gives my girl gas!!