Sawyer throws his engagement ring for Juliet in the ocean

Kate finds Sawyer sitting on the dock. He tells her that it's his fault that Juliet is dead, not Kate's, because he convinced her to stay on the island in 1974 because he didn't want to be alone. He delivers the devastating line "I think some of use are meant to be alone."

He the reveals that he was going to ask Juliet to marry him and we see him holding the ring which he pulled out of the box (see that here). He then throws the ring in the ocean, tells Kate that she can make it back to the temple by night and leaves her there, where she breaks down.

Just a little editorial note: Josh Holloway delivers a stunning performance in this scene that rivals his excellent work in season 5.