Regular polygon disk

Use n+1 vertices and n triangular faces.
Vertex n is located at (0,0,0).
Each vertex 0 <= i < n is located at (cos(θ),sin(θ),0), where: θ = 2 π i / n.

The normal for every vertex is (0,0,1).

Faces are the n triangles: (0,1,n),(1,2,n) ... (n-2,n-1,n),(n-1,0,n).
Notice that all the faces contain the center vertex n.

Cylindrical tube

Use 2n vertices and n rectangular faces.
Each vertex 0 <= i < n is located at (cos(θ),sin(θ),1), and
each vertex n <= i < 2n is located at (cos(θ),sin(θ),-1), where: θ = 2 π i / n.

Surface normals are (cos(θ),sin(θ),0).

Faces are the n rectangles: (0,n,n+1,1) , (1,n+1,n+2,2) ... (n-1,2n-1,n,0).

Cylinder

Use two polygonal disks and one cylindrical tube.
Translate the first disk by (0,0,1).
Translate the other disk by (0,0,-1), and scale it by (1,-1,-1);

Superquadric

Start with a sphere mesh.
Choose some power p. p=4 gives nice looking shapes.
For every vertex:
    - compute S = (|x|^p+|y|^p+|z|^p)^1/p.
    - divide the x,y and z coordinates of the vertex by S.

Regenerate the mesh normals.