So unique, one runs into walls, trips up stairs, falls of tall places, etc.
Also, one who asks self-answering questions, or the Captain Obvious phenomenon. Those who wear hats backwards in the sun and still hold up their hand to shield their eyes and squint at subjects at a long distance. Pretty much anyone who looks at their watch, and when immediately asked what time it is, they glance back.
When someone refers to themselves on another as special, the correct retort is a sarcastic, "Like wear a helmet all the time kind of special?" Hence the term Helmet Special is a way to refer to someone who should wear one. All the time.