I'm working on a fic involving two of Shining Armour, but I'm having trouble figuring out how to distinguish between the two versions of him. Only one of them is really him, and both start out male and end up female. Any suggestions?

Have the clone called by a nickname like 'Shiny' instead of 'Shining Armor' and have it as 'Gleam' instead of 'Gleaming Shield' later.

Depends on the perspective. If you're using a third person omniscient, I recommend having Shiny and Shiny 2 decide on a name right off the bat. If it's third person limited, just have it in Shiny's head. If you're doing first or second person, you don't even need a name. In any case, unless you want to make physical changes to Shinydick number 2, you can just call him an alternate name that's still recognizable, like white knight or something.

3827416 That works, though I'll have to have the real Shining go out of his way to refer to the double as such.