I've got this crazy obsession. Whenever I step out of my house, and it's sunny, I remove a cap from my bag, and wear it!
Previous night, I choose what t-shirt I am wearing the next day, and accordingly put a cap in my bag. If it's a sporty t-shirt, I keep my white Nike cap (the one I am wearing in the photo) in my bag. If it's black, maybe my grey Woodland's, and so on.
Caps are better than sunglasses, I feel. They cover your 3/4th of the face, just leaving behind the chin area. (Plus, you can hide your face while you're randomly laughing while walking alone. I sometimes observe some funny things that are common in the people that walk pass by me, and laugh real, real hard. So caps can hide your face while you are laughing stupidly on roads!)
What do you prefer? Caps or Sunglasses? Also, what are you obsessed with?