Another hardy fish that is not very common but is very active is endlers livebearers, Poecilia wingei. They are great looking, hardy and very active. My wife describes them as looking like guppies on speed. They need a temperature in the 70s F, most any typical tap water will do for hardness and pH. The only problem with them is that if you get a few in a reasonable sized tank, you will need another tank in a few months to house the offspring. My avatar is a poorly focused picture of one of my endlers, they won't hold still for pictures either.
To go with the endlers, I would get a small shoal of any small corydoras like the paleatus, skunk cories, panda cories or most any of them. They are also very active but tend to keep the lower part of the tank moving.
Of course, as you would expect, these are some of my personal favorites.