I only have a couple...
I talk to Twende a lot, haha, so he understands some hand movements when I'm on the ground.
While on the ground...
"Come here!" -...come. He'll walk right over.
"Whoa!" - Stop.
and then just random phrases and such that he has put to actions.
While on him...
and again, other phrases.
When I was younger, I rose a push-button horse for my lessons, and when I started cantering, I said, "WHOA" as in, whoa, this is cool, and the horse halted completely.
Twende isn't that good yet, ha, but he's really good with whoa.
"Yes. Like 'Wendy'...With a T."