I am currently studying the applications of games in quantum information theory and related fields and I am aware of its uses in places like model theory and set theory. So I was curious, what are some other somewhat surprising places(somewhat because I am aware of the subjectivity of the term) where games were/are useful tools?



Surprising applications of the theory of games?
I think evolutionary biology is a major application, if you're accepting answers outside of math. The central notion of an [evolutionarily stable strategy (ESS)](https://www.siue.edu/%7Eevailat/ev-gt-simple.htm) is a Nash equilibrium.


