Ok, this one's basically come as a random from thought from being a bit of a closet "how to train your dragon" fan.
I find the "universe" created there to be a rather awesome place.
Considering how well the human race has done with husbandry (taming and training animals to work with/for us) it begs the question of how differently the human race might have developed if we had an animal as widespread as the horse with a similar character (friendship/loyalty or just straight trained obedience) that was able to bare us and take flight.
The use of roads and air travel would likely have been MUCH reduced. Walls would be a pointless obstacle by means of basic security and each tribe/race/country of early humans that tamed these creatures would have had a MUCH wider traveling range (so we'd have all been rather more mixed earlier on and perhaps less chance for isolated tribes to found individual religions/social traits). Being able to see the ground from on high may well have improved our overall sense of ecology too along with a likely VAST reduction in fossil fuels used by cars etc.
With earlier individual flight almost a matter of course it's also much more likely if/as tech improved we'd have individual flight-based technologies.
The differences such a "trivial" change in planetary species would have made seem quite staggering.
Thoughts?