There can be no such shape. If there were a shape with n flat surfaces, then if you sliced off one vertex, you would have a shape with n+1 flat surfaces. So it is always possible to add one more flat surface.
It is a cube or a cuboid
There is no such shape.
There are two definitions for 'cuboid', but they both describe a shape with six flat surfaces (or 'faces').
A triangular prism has 5 flat faces.
a sphere, of course!
a cylinder l
Squares, rectangles, and the rhombus.