Renaming

For a transformers, a name is not just a way to design someone, it's almost a way to describe itself. To the point that some transformers can even change their name if their body go through big enough changes. In plus, those name's changes can also mark the obtaining of new powers or more responsibility.

G1
The most famous case are the Matrix's bearers Optimus Prime, previously know as Optronix or Orion Pax and Rodimus Prime previously know as Hot Rod.

An other famous case, but more debatable, is about Megatron/galvatron.

Other cases are:

A3/Alpha Trion Ariel/Elita One Bumblebee/Goldbug

Beast wars
During the beast era, renaming is far much common as when a transformer assumes the form of an animal for the first time, he generally change its name to fit its new form. But more exceptional events can still happen that leads to a name's change such as when Optimus Primal absorbed the spark of Optimus prime and became Optimal Optimus.

It should also be noted that in the Japanese continuity, each general get the "convoy" suffix, but it is unknown if it is just a tittle or a truly part of their name.

Unicron Trilogy
During the whole Unicron Trilogy, Megatron has regularly changed his name to Galvatron and gone back to Megatron.

other case are:

Overhaul/Leobreaker