At least two mate

Anything

Dodo birds?

Anything

What about things that don't exist

Although I think that might also be classified as beastiality. Also aren't they extinct?

Things that don't exist? Imagination dildo!

You mean my fingers?

Well they could work as a tool for the imagination dildo I'm sure.

This thread got better

Knives and nukes are the only true way to go. Anything else is for pansies.

How about Russia? Could I use the entire nation of Russia as a dildo? Or perhaps a Kia? Maybe even... A dildo?

Can I use someone else's head as a dildo?

If they consent sure. Just make sure you use a lot of lube, and unless you plan on killing them maybe work out away they can breathe before hand.

I mean I don't know about the logistics of the entire nation of Russia fitting into your orifices, but if you believe you will succeed so go nuts.

Like I said, only if you're brave enough