[schlagwerk]

As someone who really only cares about the mecha over the actual series: Magiking.

Very unique transformation, wings built in to the design, even its sword is a combiner, dragon mode, and just a beautiful paint job (doesn't hurt that I own the Complete Edition). It manages to override my love of cluster final combinations like EngineOh G12 that utilize all the mecha of the series. Also being away from Power Rangers since Turbo, seeing Magiking is what got me into collecting DX mecha (for better or worse).
I also think it's pretty awesome that the individual "mecha" are actually gigantic magical avatars as opposed to piloted or sentient vehicles.

I'm a huge fan of Wolkaiser, as well.

EDIT: And Magiking has a hat!