A cereal box or a t.v. [not flat screen] or a book.
any box of tampons
A solid brick is a rectangular prism. (this one example of many)
A foreign brick.
roof
A building would be a perfect example. If you simplify the details of a building, it becomes a rectangular prism. If you specifically mean a "square" prism, that would be a cube, an example of which would be a Rubik's Cube or a few dice.
Roof of a house
tent
Both a rectangular prism and a cylinder are three-dimensional shapes that have volume, meaning they occupy space. Additionally, they can both be defined by their dimensions: a rectangular prism is characterized by its length, width, and height, while a cylinder is defined by its radius and height. Both shapes can also be used to represent real-world objects and have applications in various fields such as architecture and engineering.
find
A square box. A special case is a cube or playing die.
A basic camping tent, a house roof, and the iconic Toblerone box.
A pencil.