The baseball ball.
Start with a cube. Add a meshsmooth, set iterations to 0, select the edges as shown (pic1), set their crease to 1 and iterations back to 1 and add an edit poly (pic 2).
Select the four polys and scale them down to 50% along the Z axis (pic 3). Select the two edges in the middle and scale them to 50% too (pic 4). Repeat the process for the other side but scale along a horizontal axis this time.
Spherify + meshsmooth (2 iterations) + spherify (pic 5).
Add an edit poly. Select the edges that separate the two parts of the ball (pic 6) and hit split. Your ball should now be made of the two correctly shaped elements (pic 7).
Select the two borders, make a selection set and shift-scale them down to about 95%. Retrieve you selection set, scale them up to about 105% (to make the
lips bulge a little) and chamfer them about half the width of the new polys (pic 8).
Add a final meshsmooth (1 or 2 iterations) and a last spherify to control the depth of the seam, et voilà (pic 9).
(With the last meshsmooth, you better select all the edges and force the crease value to 0, as it is likely to get it from a previous meshsmooth and produce some weird artifacts here and there).