Formal:
* Talvez: This is the most common and neutral way to say "maybe". It's appropriate for most situations.
* Possivelmente: This means "possibly" and is more formal than "talvez".
Informal:
* Quem sabe?: This literally means "who knows?", but it's a common way to express uncertainty or possibility.
* Pode ser: This means "it could be" and is more casual than "talvez".
* Acho que sim: This means "I think so" and is a way to express a tentative agreement.
Other:
* Provavelmente: This means "probably" and implies a higher likelihood than "talvez".
* É possível: This means "it's possible" and is similar to "possivelmente".
The best way to say "maybe" in Portuguese depends on the context and the level of formality you want to convey.