In comments Michael asks "What rings your cherries, art-wise?"
You think I'm gonna turn down encouragement like that? I'll confine myself to the last 100 years or so, and to painting. Here's a taste:
Umberto Boccioni. Boccioni is better known for his sculpture, but I prefer his painting, myself.
Marcel Duchamp. Astonishing as both an artist and a person. Controversial for exactly the right reasons, in that he made work that simply couldn't be ignored. If you're into reading biographies you should try one of him, there's a thousand fascinating stories. One of my favorites is that Peggy Guggenheim, the great art patron, was trying to decide if she should sponsor Jackson Pollack, essentially saving his career (and probably his life). So she sent Duchamp to investigate. When he came back and said "Pas mal," she immediately arranged for it to be done; coming from Duchamp, "not bad" was praise high enough to risk thousands of dollars on.
My tastes are influenced a great deal by the fact that I had a membership to the Art Institute of Chicago for a couple years and went at least twice a month or more. I love many more obvious artists, of course, your Gauguins and your Picassos and your Braques and your Pollacks. And if we expanded the parameters to other time periods and media, obviously, there'd be tons. While I don't consider myself big fans of their work, I frequently find myself defending the credibility of Andy Warhol, Salvatore Dali and Rene Magritte. Like many people, I'm sorry to say that my knowledge only runs up until the last couple decades of the 20th century, and I'm woefully uneducated about living working artists. You may be interested in my defense of conceptual art here, and my defense in theory (if not in practice) of Damien Hirst here.