*on the recent Littlepip question/art* Horse lips are actually prehensile in reality; and in the MLP 'verse, they're even more functional due to the user having a sentient mind to make use of them. Not to mention divergent evolution to go along with it. So, actually, it would very much be like using your hands, although certain things like firearm recoil would need to have the handles designed to compensate, lest ponies break their necks.. Magic/energy weapons would lack that issue, of course.