I keep a few soy sauces on hand, but Kikkoman is my go to. I use a few jugs of that each year just when making jerky.
Yamaroku make a traditional barrel aged one that makes a great finishing/dipping sauce. It's also da bomb on ice cream. It's 5 to 10 times the price of Kikkoman , but is well worth it.
Avoid chemical soy sauces. Check for that if you are buying store brands.