In First Year, Harry gets his Own Grow your Own Warts kit... if he snuck that into food or drink, Warts would have appeared in the Dursley's Throats and killed them. He could have gotten rid of the kit and never been suspected for their deaths,... just saying.

Sounds silly, but I want to see that Harry... one who uses posions from magical and muggle world to kill his enemies... That would be great.

Love, your Ninja Overlord, Mika.