Riding your bike to work every day gives the words "great pants" a whole new meaning. If the pants are designed not to tug or pull in the wrong places, like these Betabrand Bike to Work pants, well, that's half the battle.
Reflector tape inside the cuffs and reflector back pants pockets (you pull the reflector-edged pocket liners out for visibility) are just gravy. ($90)
Photo credit: Betabrand.