In the manga Inuyasha, the heroine Kagome acquires the ability to force the titular Dog-Yokai to fall over by saying 「おすわり」.
I figured this must be a typical dog training command, but I wondered why it was not a more direct comamand such as 「すわれ」or at least 「すわって」.
I haven't studied Japanese in a while, but I didn't realise this was a verb form at all. I thought that "pre ます" form didn't have any grammatical function without ます, and adding the polite initial-お seemed strange when talking to a dog.
Sure enough, according to this question Japanese Dog Training Commands
most other commands are in a direct imperative form, so what makes おすわり special, and what shades of meaning does a verb in "お-verb-り" form convey that すわって、すわれ etc do not.