This is the custom mashup transforming AT-AT/Optimus Prime toy created by custom toy maker Spoonman. I'll be honest -- eight year old me would have killed for that thing. "Only eight year old you?" *brandishing ninja sword* Just show me who needs the pointy end.
Keep going for a bunch more shots in both AT-AT and Optimus Prime forms.
Thanks to Joshua S, who informed me he still has all the old metal Voltron toys and may or may not have just made me jealous enough to meet my blade.