List of things Optimus Prime transforms into

[Sky Shadow]

Debatable:

A bat - Technically, the first release of both Beast Wars Gorilla Optimus Primal and Bat Optimus Primal count as Optimus Prime, as they were released before the cartoon (which established Primal as a separate character), and the accompanying fiction indicates it is the same character as G1 Optimus Prime. It is notable that the TF Wiki uses this logic (but also lists both as Optimus Primal). It is also notable that our founder here at Ozformers disagrees

I can't see how this is debatable - if you count Star Convoy, Gorilla Primal and Optimouse Prime, then Convobat/Bat Primal is a no-brainer.

[Demonac]

Don't forget the transforming gift card from Target that was given out at Botcon.