Nikutai Teni is a favourite for many of us
It includes multiple bodyswaps, although just one male character who ends up in the body of two different girls in the first part and one other in the second. The “realisation scene” has everything; looking shocked in the mirror and doing a nervous inventory of his new body followed by going to the toilet as a girl and the discovering of a woman’s pleasure. It is also out if both sub and dub.
The story centres around a school archaeology club who get trapped in the school building by a force field around it which also seems responsible for the team swapping bodies.
There are two parts to Nekutai Teni. The first part is focused on the perspective of the male character. The second part pretty much tells the story again, but from the perspective of one of the female characters, Sakajou.