i don't really have a favorite, but zules mentioning umbreon made me think of this (and then spend most of an hour drawing it): View attachment 3183
(also i just realised that the head is too big, but im too lazy to fix it)
Fun fact: Prior to generation 4, Flareon was one of (in terms of battle strength) worst eeveelutions. This was because although it had a good attack stat, it couldn't use it as effectively because all fire type moves were considered Special (non-physical). It was the only eeveelution that had this problem.