Most Common Coins

I can't find any coin with a rarity index lower than 3, which is the US Lincoln Memorial 1 cent. I can't think of anything more common than that. The United Kingdom Penny is also at a 3. What coins have a rarity index of less than 3?

This was discussed many times, for example:

• https://en.numista.com/forum/topic79706.html
  
• https://en.numista.com/forum/topic82993.html
  
• https://en.numista.com/forum/topic66448.html
  

You can use forum search function to find many more similar threads.
Interestingly enough, lowest rarity index decreases with time. Previously the record was 5, now it is 3.