I find that it is quite titilating to overhead slash the cav as its charging straight at you. I feel cool doing it.
Just stand still, and stare down the rider as he gallops towards you. Hold your ground, gritting your teeth and clenching your genitalia in concentration. At the last moment side step ever so slightly, and bring your weapon down upon the charging horse's head. My god its so awesome to do that successfully--you feel like a jesus.