The man without a memory. He has no memory of the past and also cannot form memories. For all intents and purposes, he's not conscious, is he, in the literal sense of the word? I've always wondered how I would be without any self-consciousness. How much of who I am is because I remember who I'm supposed to be? I've absolutely no idea, but he seems fairly happy, all things considered.
Fortunately for him, he recognizes one person, his wife. I'd recommend watching how he interacts with her. It's not a long video and I'd suggest watching at least to the point where they explain that every time he sees his wife, he believes it's the first time he's seen her in years. It's kind of sweet that he reacts like that totally unaware that he does it presumably every day.