Formal:
* "C'est mon père." (This is my father.)
Informal:
* "C'est mon papa." (This is my daddy.)
* "C'est mon père." (This is my father.) - This is also used informally, but it is more common to use "papa" in this context.
You can also use "papa" in a more affectionate way:
* "Voilà mon papa." (Here's my daddy.)
* "Regarde, c'est mon papa." (Look, it's my daddy.)
The best way to choose the right phrase depends on the situation and your relationship with the person you are speaking to.