Colonel Santos Benevides and his Texas Cavalry comes to easily to mind.
But, Texas is also stuck with Adrian Vidal and his Partisan Rangers. Vidal started out fighting for the Confederacy, switched sides, deserted again, and crossed over into Mexico to fight the revolution with Juan Cortina. He was eventually caught and executed by the Mexican Imperialists.
The Oklahoma Cherokees, now that I thank of it, also contributed a regiment to the Confederacy.
Jews also fought for Apartheid, and against it.