A couple of strong men can wrestle a horse to the ground, so I didn't understand how a thin line of warhorses could machine gun hundred of orcs off of the ramp in Helm's Deep like that (speaking of the film).
Horses are massive animals. Once you get armored cavalry moving they can be devasting to troops on foot. That scene was much more realistic than you think. 'There are older and fouler things than Orcs in the deep places of the world.' - Gandalf the Grey, The Fellowship of the Ring