The Forge, ENT 4
Good Lord, the amount of Fan Service in this episode (”Who said logic is the cement of our civilization, with which we ascend from chaos using reason as our guide?”) is absolutely unreal. And awesome. And so is the whole episode, which posits that that pain-in-the-ass Vulcan High Command has been corrupt this whole time (I knew it!) and Vulcans need to change in order for TOS to make sense.
They got our letters!