Mait Muntel, Founder at Lingvist. This is his first startup and he's already attracted over 1/2 million beta testers (without a single bit of marketing). If that's impressive, how about getting the co-founder of Skype as an early investor? 

Mait left the team at CERN, who discovered the GOD particle, to start this startup. It's an inspirational episode. 

Resources: Website  / Linkedin