title_body: What’s the drinking game with thumb on the bar?
upvoted_answer: I believe in the U.K. there is one called “Tom Thumb”, basically:
  
  
  someone is allocated as the “Thumb Boss”
  everyone in the group must watch them
  when they place their thumb on the bar everyone must follow suit. 
  The last person looses and has to take a good measure of drink. 
  Usually this person then becomes the “Thumb boss” and they start over.
  
  
  I never found it especially fun, other more subtle games were more entertaining.
  
  There is a better description available here.
  
  I would also add there are other games with fingers involved, usually everyone touches the table/bar and the first to move their finger looses etc (basically the reverse).