First: Just so wrong!!! Second: Illegal!!! Third: The suggestion that animals from the pound are worthless and there for usable in sexual games is horribly offensive. If an animal is at the pound, means it has suffered at the hands of humans already.
Holy cow, chill already. Don'tcha recognize a joke when you see one? Was it offensive of me to suggest that we use an innocent cow in a religious reference without it's informed consent?
In reply to the OP, definitely the Venus 2000. There's a recent video clip of a domme bringing her male sub to multiple orgasms using one. I don't have the link at my fingertips, but you can probably find it easily if you search. I'll post it if I run across it.
The problem with the Venus, as others have mentioned, is that it's damn expensive.