I once had a dragon fly circles over my head for several minutes and then swoop down to attack a Thalmor death squad that I never even saw coming.

Best part was, they kept trying to kill me with ranged magic while the dragon was attacking them. Smart dragon, stupid Thalmor. Sadly my follower was also a ranged magic expert and he went nuts on the dragon and killed him, if I'd been alone I probably would've hidden somewhere and let him go his merry way provided he didn't attack anyone I cared about saving.