Formal:
* Quelqu'un (pronounced "kel-kun"): This is the most common and neutral way to say "anyone".
Informal:
* Quelqu'un (pronounced "kel-kun"): This can also be used informally.
* N'importe qui (pronounced "nahn-por-tay kee"): This literally means "no matter who" and conveys a sense of "anyone at all".
In a negative sentence:
* Personne (pronounced "per-sun"): This means "no one" and is used to say "anyone" in a negative sentence. For example: "Personne n'est venu" (No one came).
The best way to choose the right translation depends on the specific context and the formality of the situation.