My favorite types would be...hm...
Electric, for certain. O_o For some reason, I like the thought of the whole electrical element...
Bug, maybe. But only because I've found myself liking quite a few bug pokemon for their looks (ariados, nincada and ninjask, butterfree and beautifly, among others)....
I also like the Poison type a little, only because I absolutely love both nidoran evolution lines. :P Now only if that poor type was better...