What is a shape that could be the cross section of a cone?

The cross section of a cone can be a circle, an ellipse, a triangle, or a parabola, depending on how the cut is made. If the cut is made parallel to the base of the cone, the cross section will be a circle. If the cut is made at an angle to the base, it can produce an ellipse or a triangle, while a vertical cut through the apex can result in a triangle.