Any name which isn't a human name would be inherently unisex, I'd think, not to mention some human names like "Fran" or "Joe" or "Pat", which would work fine for a rabbit (there's a book called "Pat the bunny", isn't there?).
My first rabbit was named Scone MacBunny - his first name could have been either a biscuit or the place where Scottish kings were crowned, but wasn't inherently one gender or the other. Any food or plant name would be unisex - Carrot, Parsley, Twig, Leaf, Hay, Clover, Hazel (usually a woman's name for humans, but Hazel the main character in Watership Down was male), Maple, etc. The same would be true of most place names - London, Montana, and so on.
Some of the common rabbit names are not gender specific - Thumper, Ears, Easter, Cadbury, Binky, among others.
You could also look at nationality - I'm drawn to Scottish names for some reason, maybe because of Scone, so what about Lugs (Scottish for "ears"), or Rabbit Bunns ("Rabbie" for short). Scone is a place name in Scotland, so is Fife, Stirling, Falkirk, Blair (Atholl, amongst others), Islay, Skye, Arran, Iona - any of those would be a good name. If Ireland interests you, what about places like Mayo, Tara, Wicklow, Kinsale, Dublin (I kind of like Dublin O'Bunny as a name), Galway, even Dingle? There's always Pat O'Bunny, or Bunny McRabbit, or even Lag O'Morph...