Formal:
* Bien sûr: This is the most common and versatile way to say "of course". It works in almost any situation.
* Naturellement: This is a slightly more formal and elegant way to say "of course".
* Certainement: This translates to "certainly" and is another formal option.
Informal:
* Bien entendu: This is a less formal way to say "of course", but still polite.
* Évidemment: This is even more informal and means "obviously".
Other options:
* Sans problème: This literally means "no problem" and can be used to mean "of course" in some contexts.
* Pas de problème: Another way to say "no problem" that can be used to mean "of course".
The best choice will depend on the specific situation and your relationship with the person you are speaking to.