A  horse that is calm, doesn't spook and is very obedient may be referred to as a packer. It sounds like a negative term, but if you are looking for a quiet riding horse, the promise of a packer in an advertisement may indicate a horse worth looking at. Packers are usually horses that even non-riders can enjoy, because they are safe and will put up with a lot from an inexperienced rider. 

Use:

She bought her husband a packer.

 

Also:

Bomb proof, husband horse