What magical horse sprang from Medusa’s severed head?

Pegasus

What famous gaming magazine abbreviated as 'EGM' started publishing in the late '80s? What's the name for a trained medical professional who takes care of teeth? What space-faring group does Yondu Udonta belong to? Which team originally drafted Scottie Pippen before trading him? What river forms part of the border between the United States and Mexico?