Guppies, Dwarf Platies, and even regular Platies would work. As long as you aren't breeding them and can guarantee you have females that aren't pregnant, these should work.
nothing to add that hasnt been said before really, no swordtails or mollies, 10 gallon with 4 danios and 1 platy. maybe add one or 2 more platies. or instead, a few pygmy cories or shrimps. not only fish can go in an aquarium