I haven't seen the Least Killifish
(heterandria formosa) listed
Native to Florida i believe, males get just under an inch and females maybe 1 1/4 inch. These are livebearers and are super easy to keep. Parents will not harm fry. Some people think they are kinda plain looking, but they are very fun fish to watch. Doubtful you'll find these in your LFS though. I really love these tiny personable fish! I've had mine for almost a year now.. easily take any food provided (as long as its small enough) and will even forge for algae.
Here's a Video of them :