Any micro usb cable will work, like this one. https://www.amazon.com/Monoprice-6-Feet-Ferrite-Plated-105458/dp/B003L18S0E/
Check out this tread on the Galaxy S6 subreddit for both a discussion on the topic as well as a link to an excellent choice for USB cables. The cables can be purchased through Amazon as well as the Monoprice website, but if you go that route be sure to buy them direct from Amazon or you run the risk of getting low-quality counterfeits.
Whatever you buy, the cable needs to use 24 AWG or heavier wire for the charging connections or else quick charging won't work to its full potential.
Would this be a good data cable to get? I'm not sure what a "good" data cable is. I too get the constant calibrating message with my original fast charging cable that came with my s6.
Edit: For those with the constant calibrating message while using the original samsung charging cable (s6 for me), I bought this cable and no longer have an issue