Ski goggles also can be useful. In summer sun hat, sunscreen and sunglasses are advisable. To power yourself up hills requires lots and lots of energy. Fluids are also very important to remain hydrated. It is a good idea to carry at least a litre of water or juice though this is quite heavy.
Hot drinks can be very morale boosting in winter.
Carrying some emergency food e.g. some chocolate is advisable. It's pretty essential to carry a whistle and a survival bag - bright, orange plastic bag to shelter in during an emergency. It is also a good idea to carry at least a simple first aid kit. A torch is very useful especially head torches that allow you to keep your hands free but still direct light where you are looking. It is recommended that you carry these and use them so you always know where you are.