Can you? Sure. Is he going to like it? That depends on both his preferences and on how you use it. If he likes being penetrated, well, a rabbit has that capability and the same thing goes for vibrations. All that being said, a rabbit just doesn't seem ideal for use on a man. For a woman, the little rabbit part is great for clitoral stimulation during penetration, but if you're using the rabbit to anally penetrate a man, I can't see where that little rabbit would go without being dreadfully uncomfortable. So sure, in a pinch you could use the rabbit for anal penetration, but if you go too deep, those little bunny ears are going to start jabbing him in the scrotum. Unless he happens to be really into scrotum-poking, you're probably better off finding another toy.