I like pretty much anything native, especially fox snakes (though they're illegal). I love the western ssp's of sirtalis, especially the Oregon red-spotted garter... from books I really like narrow-headed gartes though I've never seen one. Salt Marsh Snakes are really cool as well.
My #1 aspirational snake has to be the mangrove, though the thought of a bite bothers me a bit.
Right now I have a mud snake and they are one of the most interesting snakes around... I'll just have to wait and see if it becomes my favorite.