Love my new MacBook, but OS X is still new to me...

Two weeks ago I got a great deal on a MacBook Pro with Retina and I am loving it. The hardware is absolutely stunning and the experience is so smooth all of the time. My only complaint is that OS X is still new to me. I feel as though, for what I've used it for, I might as well have spent the money on a Chromebook Pixel. I am just so not used to OS X that I've been pretty much only been using Safari, iTunes, and that's it. So, seasoned OS X users, what do you do with your Macs? I don't care if it's edit photos, write term papers or code-- whatever. What's some great apps for Mac? What's some great hidden features of OS X?