i'm probably gonna sound rude, but you did come here with literally just "hey, i'm a guy who wants to fuck any animal. which one?"
with that said, if you're looking for any animal just to have sex with an animal i heard bad dragon has fairly wide selection of dildos and masturbators.... don't ever get any animal for the sole purpose of having sex with him/her. not only is it wrong on so many levels, but what would you do if said animal had no interest in having sex (it is a possibility) with you? just get rid of him/her and try again?
edit: this not being the very first response you got is quite sad, animals are not sex toys to go "which should i get?"