It's rare for penny stocks to find their way into mainstream attention — that is, unless a familiar name enters the equation. That happened when Mixed Martial Arts Group Limited (MMA) announced that it has completed a private placement worth $3 million, led by American Ventures, with contributions from Donald Trump Jr. The development saw MMA stock go on an upward trend as trading volumes soared at the onset. Of course, any speculative investor would be attracted by the headline alone. But celebrity-fina ...