I'm inclined to think it is a male Melanotaenia praecox. They tend to vary a little bit in colour and it is hard to assess the quality of digital images - but I think it might be. I have a couple 2 feet from my desk here in the office and some more in other tanks. For more information about this Rainbow and Rainbows in general:
I got some of these a year or two ago (I have since gotten rid of them). I tried getting an ID from members on the rainbowfish mailing list as well and they agreed it was "Australian rainbowfish." The local Wal-Mart has tanks FULL of them--exactly like the one you have pictured.
Basically, what you've got is the mutt of the rainbowfish world. I wouldn't attempt to breed it unless you want to keep the fry for yourself or your own enjoyment. This is one of the only commercially bred species of rainbowfish in the hobby, and the lines have been inbred (and most likely hybridized at some point) that it's impossible to know if what you have is indeed a pure species or not. I would say there is a 99.999% chance that it's not.