How much trouble could I get into if I sell shirts with “Gary Oldman is Awesone” or Gigli wasn’t that bad” printed on them?

Will you be putting photos of Gary Oldman or Affleck on the shirts? Because there are laws prohibiting you from making money using another person's likenessi.e. image. Whereas, movie titles usually cannot be trademarked.

The California Right of Publicity law says that if you use another person's name on merchandise without their permission, you can be liable for any damages suffered by the person and/or $750, plus any profits you made. Also, punitive damages are possible and the prevailing party has to pay the other side's attorney fees. That's a heft amount of money for a joke almost no one is going to get. You can, however, asks Gary O for his permission to use his name on this shirt. He might say yes. As for making a shirt with the name of the movie "Gigli," that in itself would probably be fair use as commentary on a movie. However, "Gigli" is a trademarked name of a line of products unconnected to that movie. You may run into trouble with the owners of that trademark.