The excellent geekery blog Geek Tyrant introduced me to the work of Spoonman, a custom toy maker, with this Optimus Prime who transforms into an AT-AT. It's called "AT-ATIMUS."
I was initially going to just post about that transformer, but as I scrolled through Spoonman's Facebook gallery, I saw more and more amazing custom Transformers by him/her.
I found this mashup of Cobra Commander and Starscream even more delightful when I learned that both characters were voiced by the same actor--Christopher Collins.
Spoonman doesn't offer much information in his gallery, but this appears to be an ichthyosaur version of Sludge.
This is one of my favorites! It's K.I.T.T. from Knight Rider!