(this is the last of my unknown components).
It is less than 1 cm (half inch) diameter, has one wire on each end.
It has description:
CNR C8G 75L RU G12
The RU is written reversed.
What you're looking at is almost certainly a Gas Discharge Tube, or GDT for short. They are basically a spark gap inside a sealed chamber filled with a specific inert gas mixture -- this allows them to provide more precise protection than an air spark gap. They're used for the same things as spark gaps, though -- mostly, overvoltage protection as when they break over and start conducting, they will "crowbar" the overvoltage.