A 3D shape with one base and three faces can only have triangular faces.
Pyramid with a hexagonal base
most likely a triangular prism
There are 2 triangle base faces, and 3 rectangle faces. 5 total faces.
A hexagonal pyramid
A Triangular Pyramid, 3 faces, 1 base.
A triangle with an approximately spherical shape on top, is one possibility.
If the triangles are congruent then it is a triangular-based prism.