What is the best social amplification / brand ambassador tool?

I'm looking for a tool to make it super easy to share social messages through the personal and professional networks of employees and other brand ambassadors. I've found quite a lot, but they are either complicated and aimed at large enterprises, not in active development anymore or way too beta to use with external stakeholders. What's the most simple, well developed and easy to use tool to do this?
Posted 
Your recommendation
🤓 Have a recommendation? Join to share.