I would love to see some kind of god related to thievery. Maybe not straightup THE GOD OF STEALING but a god that loves gold, appreciates cunning, and reward avarice. There are no direct alters to him or out and out priests of his order, but if you follow his "tenets" then eventually he gives you a sign.
I've also always had a soft spot for lesser gods that represent various niches in the world that are less obvious but still everpresent, for example:
-The god of baking
-The god of board games
-The god of blacksmiths
-The god of falconry
Although as I type this I'm starting to feel like it would be better to just wrap those ideas into larger gods, like the god of fertility would also happen to have a lesser baking aspect only worshipped by a loaf-cult in the grassy lowlands of some kingdom.