I have the horse mount from The Immortal Flames. I can't use it unless I swap back to the Immortal Flames, but I'm working on getting the one from Limsa's GC. Same for the chocobo minions that you can get, and the barding, even though there's achievements for having all from all GCs.

Kinda weird you can't show off stuff from other GCs, when they've flat out admitted they don't know what they want to do with the GCs.

Plus we kinda saved all their asses, so everyone knows we're technically allied with every big nation/ect, so why not just let us rock what we want from them?