I can't really pick just one, there are so many different great people on steem...
I admit I'm a bit biased especially cause he is my father, but first I would say @irvinesimages and even if he wasn't my father he still posts some really amazing photography which I think deserves more attention/recognition.

And... I hope no one would be unhappy with me for not mentioning them, though I'd next give a three-way tie to @leaky20 @ayushjalan and @bengy

There are literally so many others, but those three I think deserve a particular mention from me because I've been interacting with them a lot in recent times and because they all put out good, high quality, interesting and thought-provoking content in my opinion. Plus from what I have seen they are all very social with the people who comment on their posts and they do a commendable job of responding to people who try to interact with them.