I don't know about the best compliment, but as far as most influential....
I had been working in a tech support role for four years, knowing that I had to transition from traditional employment back to self-employment, but I was struggling to find a business model that would actually, y'know, pay the bills. Over the years, a number of completely different customers made a point of telling me, with only slight variations, "Wow, David! You have a really great voice. You should really consider pursuing some sort of career with that!"
I'll be very honest: While I might've agreed with the first part, I had never thought about actually earning a living this way, because I had pretty much assumed that the voice talent careers followed the pattern of professional sports, where there is a tiny group of very well-known and talented people who earn extremely good livings... and then there's everyone else, who don't. I didn't want to chase a very-low-probability dream.
Finally, after hearing the compliment for the umpteenth time, I figured, what the hey; it certainly couldn't hurt to at least try and test the waters. So I hung up a very simple shingle at Upwork (at the time oDesk) in October, started to build a voiceover business of sorts, and eventually quit my job in April. I still have a way to go before I'm making "fantastic" money, but for the moment, I'm able to pursue a few different self-employment avenues, plant seeds, diversify income, and, y'know, pay the bills.