Simple and light, but works surprisingly well - Spec Ops Recon Wrap Multi-Season Multi-Mode Head Gear

Now this is a pretty good face mask. Used it during -15 degrees Celsius outside and although it's a very lightweight and breatheable thing, it traps the heat of your breathe quite effectively. Coupled with a cape of my jacket and a pair of tactical googles, it protected my face well enough from the cold and snow.

Although during colder days I'd need something warmer, the very fact that it's breatheable allows you to wear it during wider range of temperatures.
Pros: Gives you a good protection for its light weight
Cons: In some situations I'd need something made of warmer material

This review was written in the old system and had content requirements that are different than reviews written today.