I've always been a fan of graphic tees. I have plenty of old t-shirts stashed into my drawers because they're incredibly easy to wear and they never go out of style. You can pair a graphic tee with just about anything and it will bring a complete different edge to an outfit. At the moment I'm really loving animal graphics a la Givenchy or band tees. They look really cool paired with girly or structured pieces like skirts and trouser pants; it creates the perfect contrast between casual and dressy.