In Book 1, in the first battle between the Starks and Lannisters, there is a great battle scene where Tyrion mounts a horse, kills several enemies, is thrown off his horse and has to fight a Northern three times his size. However, in the show, we were screwed out of this battle scene, probably because of budget issues, so instead all we get in the show was Tyrion being clumsily stampeded and accidently knocked out by one of his own men. If I had read the book before and was expecting this great battle scene and instead got that, I probably would have been severely disappointed and I simply don't want to become that kind of fan.