But what I'm really wondering is if it is possible to have a complete sentence without a verb.

you guys make my brain happy.
sorry, Mastermind, the shortest sentence cannot be nothing at all. Saying nothing isn't a sentence, because you didn't say anything. Could I say the smallest house in the world is a bare patch of land? Could I gesture to an empty table and say, behold, the smallest violin in the world? Therefore, no sentence at all is not the shortest sentence. Sorry. Seems to me that 'Go.' wins the prize so far.

I just realized - I'm talking about nothing! ;)