Formal:
* Avec plaisir: This is the most common and neutral phrase.
* Avec grand plaisir: This adds emphasis and means "with great pleasure."
Informal:
* Avec plaisir! This is the same as "Avec plaisir," but with an exclamation mark, making it more enthusiastic.
* Bien sûr: This means "of course" and is a more casual way to express agreement.
* Volontiers: This means "willingly" and is a more informal way to say "with pleasure."
* Pas de problème: This means "no problem" and is a very informal way to say "with pleasure."
Example:
* "Would you like to join us for dinner?"
* "Avec plaisir!"
You can choose the most appropriate phrase depending on the situation.