GloFish, why not.
Originally g'engineered to express GFP (jellyfish green fluorescent protein) in the study of vertebrate development, GloFish are a patented variety of Zebrafish (Danio rerio) and glow constantly, sold as GM pets.
Juvenile D. rerio is transparent, ideal for studying mechanisms behind development and stem-cell function. It can also regenerate lost or damaged organs, inc. cardiac, muscle, and optical tissue, partially by regressing adult cells to a stem-cell state.
Also one of the few animals to have their own scientific databases, journals, and been into space.