Formal:
* Prazer em conhecê-lo(a). (This is the most formal and polite way to say "Nice to meet you".)
Informal:
* Prazer em te conhecer. (This is more casual and is used with friends or people you're not very formal with.)
* É um prazer te conhecer. (This is another common and informal way to say "Nice to meet you.")
Informal and playful:
* Que bom te conhecer! (This is a more enthusiastic way to say "Nice to meet you.")
You can also use the following phrases, which are slightly more informal:
* Legal te conhecer. (This is more like "Nice to meet you" in a slangy way.)
* Manhã/Tarde/Noite boa! (This literally means "Good morning/afternoon/night" but is often used as a casual greeting, including when meeting someone for the first time.)
Remember to choose the appropriate expression based on the context and your relationship with the person.