The Japanese Transformers installments have bullet train mecha, though they act just like other Autobots in robot form. The English name of their combined form is Rail Racer. The classic series had Astrotrain as well.
Brave Express Might Gaine is an earlier series whose mecha had a more old-fashioned aesthetic.
There's an old series whose name escapes me where the main characters were bullet train mecha who retained their train noses in robot mode, essentially just gaining arms and legs.
edited 14th Sep '12 4:44:52 PM by Recon5
The only ones I can think of are from Video Games instead of Anime. To be precise, the Strikers 1945 series, where every game has an incarnation of train-based mecha that take multiple railways at once.
What profit is it to a man, when he gains his money, but loses his internet? Anonymous 16:26 I believe...
I'm just curious about how many train-based Humongous Mecha are out there, and to what extent they keep up the "train" motif i.e. riding along on tracks, spouting steam and making whistle noises while in mecha form. I do bleev that there's new series in the works called "Train Hero."