Honey Mustard is probably number one, Ranch is well received but may be up to the taster. For me, ranch is second, followed by BBQ sauce.
After that... Sweet and Sour, Hot Mustard, Buffalo, and finally there was some sort of hot sauce I forgot what they called. None of it was bad, but I found the spicy ones less appropriate, especially Buffalo which I associate with wings.
To my knowledge, none of these are seasonal or a special event sauce, but a seasoned nugget specialist may know more.
(Outside of this, Sriracha is actually my favorite sauce for chicken nuggets, but that was not part of this particular experience.)