Rebekah Mikaelson - She receives an invite to the wedding of Rebekah and Alexander splattered with blood and the dagger engraved on the envelope
Amy Peterson - Receives a few newspaper cuttings from when she was a vampire discussing mysterious deaths as well as a vial of blood.
Sydney Prescott - Receives a ghostface mask and every time she turns on her TV/Computer for the next 24 hours she'll just hear "We all go a little mad sometimes" and "Movies don't create psychos. Movies make psychos more creative." over and over
Thor - Any time he closes his eyes or sleeps for the next 72 hours he only dreams of the 'You were made to be ruled' speech from the Avengers and flashes of the havoc Loki caused NYC
Richard Plantagenet - Is sent bloody blankets from the Tower.
Snow - Apples. Everywhere she goes there will be apples, a bushel of them as a display, people eating apples around her. And tomorrow morning an apple tree will have sprung up outside their home.
Dawn: For 24 hours Dawn will be not be able to see, speak to, anyone from her own cannon nor will they be able to see/speak to her, Think Willow on her return to Sunnydale after the unfortunate going mad incident.