I've been a longtime fan of Shepard Fairey, I have about two dozen of his prints. I also have a few T. Stout, which is more for fun. I also have a fun Tokyo print by eBoy. I like a lot of more traditional artists, but I don't want to do poster reprints so I just admire them at museums. I don't know how many people here are similar, but really fell for Mark Rothko when I first went to MOCA in LA and saw a lot of his works up close --there's something about their scale.
I like some British mod art, but some of it can also be terrible --but that's modern art in general.
I enjoy some surrealist paintings... It would be cool to own The Treachery of Images.
One of my favorite sculptors is Bernini, he was a classic polymath.
I have a nice art book of his, but if only I could afford the real deal (but then again, the best stuff is on walls...)