I'd have to say Gary, i think he's the best trainer ever seen in the series (besides elite 4 dudes). Although, i always go for ash when the battle, i find myself in awe with gary's superior strategic mind, and ability to catch great pokemon! I like how he evolves all of his pokemon, but not right away, so he can get the best out of them, i think the silver conference was just an unlucky break for him, and i'm still almost thinking taht he let ash win, so he could begin his path as a pokemon researcher that much sooner, and he probably thought that Ash was the only one "worthy" of beating him
