REGISTEEL obviously.
Licking is not as good as you think. You're eventually going to want clenching and I don't think Lick's tongue can roll tight enough for that. Steel probing, on the other hand, is immensely satisfying and wears you out enough that you need to take long breaks. You can ultimately kill yourself using it when you are done. Plus there is no legal, theological, or moral prohibition against fornicating with a metallic, genderless object, but Lickitung will obviously be morally outrageous because of the flesh, and it will start to stink and you won't be able to clean stink that is deeper than flesh. Embrace steel.
