Use a sturdy box and lots of bubblewrap and, if questioned, tell them that it's "art," "a valuable antique," or "is fragile and has sentimental value" -- whatever you feel comfortable saying (while maintaining a straight face). We were allowed to carry on an "exquisite piece of chainsaw art" (don't ask!), which could arguably have been deemed a weapon/blunt instrument.

So, make the rabbit look as harmless, fragile, and valuable as possible. Hope you don't run into unreasonable agents.