I voted: character sheet, pencil/pen (for the character sheet), and dice.
The character sheet is the character the Player is playing -- can't really play the game without it. The pencil/pen -- if you never need to write anything on your character sheet, it must be a very boring game session.
You must have dice to play the game -- either your own dice, or borrowed, you must have some at hand, and securing them is the Player's responsibility.
I almost included the Player's Handbook, but it is quite possible to play the game without the Player ever having to reference the book. I have played a few other RPGs without owning the book. And I have played D&D without ever needing to open my PH at the table. *But*, I always bring my PH with me.
Bullgrit