Most common:
* Faire semblant de (to pretend to)
* Example: "Elle fait semblant de dormir." (She pretends to be sleeping.)
Other options:
* Jouer à (to play at)
* Example: "Les enfants jouent à faire semblant d'être des pirates." (The children are playing at being pirates.)
* Simuler (to simulate, to fake)
* Example: "Il a simulé une blessure pour éviter de travailler." (He faked an injury to avoid working.)
* Feindre (to feign, to pretend)
* Example: "Elle feint la surprise." (She pretends to be surprised.)
The best choice will depend on the specific situation and the nuance you want to convey.