I'd stick to inverts for anything less than a 10. You get lots of quality shift from evaporation in these little tanks. However, I've seen clown gobies kept successfully in a 2g. I picked up a book on breeding dwarf seahorses a while back and the author recommended a few mating pairs for a 5g tank, but you'd have to put a LOT of work into keeping them fed and healthy.
Hatching baby brine every day is fine for about the first two weeks. After that it is an absolute chore and good luck finding a fish sitter if you're ever going on vacation. Then again I'm lazy and you might have more time on your hands.