1. Riding in total darkness. I enjoy the sense of solitude - lets me come into the day in a better way.
2. Riding when it is snowing. I love it. Not when the streets are rutted with wet glop, mind you. My favorite winter riding conditions are when it is warmer (hovering around freezing), the streets are wet from the first flakes, and the snow is coming down hard.
I don't miss the extra time and hassle of getting everything together and getting dressed for various conditions.