https://www.brickplanet.com/shop/18662/epic-bot
In my opinion, this face could be rare or is for sale for a limited time or a limited quality of copies

https://www.brickplanet.com/shop/18661/the-face-of-green-fire-eyes
This face could be for sale for a limited time

https://www.brickplanet.com/shop/18660/the-eyes-of-water-and-fire
this face could be from an event

https://www.brickplanet.com/shop/18428/the-face-of-evil
this face could be rare

https://www.brickplanet.com/shop/18427/the-face-of-the-unknown
This face could be used as a gift for 4 people

https://www.brickplanet.com/shop/18426/the-face-of-peace
This face could cost 100 bits and 10 credits

https://www.brickplanet.com/shop/18425/the-face-of-trolling
This face could cost 100 bits and 10 credits

https://www.brickplanet.com/shop/18424/the-angry-face
This face could cost 100 bits and 10 credits

https://www.brickplanet.com/shop/18423/the-suspect
This face could cost 100 bits and 10 credits

https://www.brickplanet.com/shop/18422/the-sad-face
this could be free