The Actualizer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of your first main phase, read aloud the name, mana cost, type line, power, and toughness of a card in your hand, except lie about one of them. Each opponent simultaneously guesses which one is incorrect. Then reveal the card. Each opponent who guessed incorrectly loses 3 life. You may discard that card and draw a card. (They can't look it up or ask for help as this ability is resolving. Nice try, though.)