Hmmm.
Well, I would recommend the Ender's Game series. But, it seems that you've read most, if not all, of those.
I only read the first of the Game of Thrones (George R. R. Martin) series, but I'm about reread it, and hopefully finish out the series. However, if you decide to pick up the book, I would say make sure you pay attention, because everything in it matters. The plot gets really 'hairy,' and if you aren't paying close attention, you'll lose yourself.
And, if you're looking for a change of pace, I would recommend Maus: A Survivor's Tale (Art Spiegelman). It's a graphic novel, but it won the Pulitzer Prize, so it's definitely worth checking out. Spiegelman works with the pictures really well, and it's awesome the details and symbolism he is able to incorporate because of the format of the novel.
Besides that? I honestly can't think of much. I decided that I would try to finish up as many of the series that I started when I was younger this summer, so my current reading list is composed of books from the Pendragon, Inkheart, Ranger's Apprentice, Redwall (though that's really only the newest book he released), The Wheel of Time, and The Fire Within series. Pretty childish altogether, but I'm hoping that I haven't missed the window where I can at least enjoy reading the books, if not get something out of reading them. It just irks me that I have left so many series unfinished.
But yeah, I guess that's my two cents. I, of course, recommend all of the series that I am rereading (well, maybe not all of them. I have yet to see how the years have changed my literary views), but I'm not diving too deep into "profound" literature this summer.