What is your horse's absolute favorite thing?  Outside of riding!  Are there treats that instantly convert your pony into an addict or liniments that leave him yawning and chewing?  What does your horse just love to have?

The answer for all three is really food. All the foods. Dijon will eat pretty much anything. I've given him all sorts of weird people food and he eats it all. Shasta is much more discriminating, but loves carrots and peppermints. Nilla is fast following Dijon in the eat anything category. 

Eating candy canes 

Although food ranks higher, an odd thing that Nilla likes is having her ears rubbed. Most horses I've known hate having their ears touched, but Nilla loves having hers really scrubbed.