A camelbak water bladder makes a perfect pillow. Just blow into the bite valve to inflate to desired thickness and lock the valve. You can leave it in the backpack or remove and wrap with clothes or a towel.
Telescoping trekking poles make great supports for a tarp when there may not be any convenient trees or branches.
A silk sleeping bag liner is very lightweight, adds a bit of extra insulation, and is very compact and lightweight. On warm nights you it may be all you need.
Many quick releases (seatpost or wheel) can be used as emergency tire levers when your plastic ones break.
Don't go crazy carrying spare parts and heavy tools. If you have a major repair job, have someone at home FedEx stuff to you or use overnight delivery from a mailorder place for any parts and tools unavailable locally.
You can make a pot cozy by cementing together pieces of a blue foam sleeping pad. Instead of wasting fuel simmering food like pasta, bring it to a boil then set the pot in the cozy so its completely contained within. The cozy will maintain the temperature and the food will cook as if you were simmering.