First up is and will always be Georgia O'Keefe. An amazing woman who paved her own way in the then male-dominated world of art, doing things unique and true to herself. I have seen a lot of her work in person, and I am always amazed at how sure of her brushstrokes she was, and at the fresh perspective she brought to everything.
Finally, a nod to the more abstract. Marcel Duchamp's cubist work has so much detail, it's hard not to love.
Everyone has certain styles and artists they love. Who are some of your art heroes?