Formal:
* Sortez! (Formal imperative, plural)
* Sortez, s'il vous plaît. (Formal imperative, plural, polite)
Informal:
* Dégage! (Informal and rude)
* Casse-toi! (Very informal and rude)
* Va-t'en! (Informal and rude)
* Foutez le camp! (Very informal, vulgar, and rude)
More polite options:
* Pouvez-vous partir? (Can you leave?)
* J'aimerais que vous partiez. (I would like you to leave.)
* Il faut que vous partiez. (You need to leave.)
The best choice depends on the situation and your relationship with the person you are speaking to.