Sword tails get too big IMO, so do bleeding hearts. The truth is that most of the commonly available fish you see at all petstores mostly do not beling in a 10g tank if you want them to grow to full isze and see their full range of behaviors. Sometimes the larger fish will live in a 10g tank, but you really miss out on a lot of behavior and the fish do not often live to their full lifespan potential.
Here are some fish that would do really well in a 10g. Remember that not all of these fish are compatable with each other and they have specific needs, so I recommend researching them if you are interested.
Dwarf puffer, microrasbora (like erythromicron and kubotai), shell dwelling cichlids (I recommend either brevis or multifaciatus), dwarf gourami, ember tetras, scarlet badis, sparkling gourami, croaking gourami, celestial pearl danio, pygmy cory (pygmaeus, habrosus, hastatus), Asian stone catfish, clown killifish, least killifish, pygmy hatchetfish, green neons, guppies, platies, otocinclus (just 2), chili rasbora, betta, and Endler's livebearers. There are also awesome dwarf shrimp and nerite snails.