I can't stand the guy my mom is dating. What would be a good prank to pull on him?
Why? Your mom is going to date him regardless of what little tricks you try to pull. All that will do is tick her off, and make him think you're a brat. You should try having an honest conversation with your mother, and explain your negative feelings toward her boyfriend. She may be surprised by your maturity, and thus more apt to listen. Pulling a prank only puts YOU in a negative light.
Grow up, and stop acting like a 6-year-old in a tacky movie.
Just accept your mom's decision, because it is not up to you.