Was Spock able to nerve pinch the Augment guarding Kirk in the the Sickbay pressure chamber in "Space Seed"? It's been a little while since I've seen the episode and can't recall if Spock pinched the guy or immobilized him in some other fashion.
The transcript of "Space Seed" at http://www.chakoteya.net/startrek/24.htm
says, "The outer sickbay door opens, Kirk waits and then tackles Spock's guard. Spock neck-pinches him."
However, it could be that with the adrenaline flowing (the Harrison and Spock fight scene), an augment could fight off a neck pinch.