What rocket league preset cars are exclusively available on Xbox?
According to the Rocket League Wikia:
The PlayStation 4, Xbox One and Nintendo Switch versions also include console-exclusive unlockable Battle-Cars (Sweet Tooth for the PlayStation 4 version; Hogsticker and Armadillo for the Xbox One version; Mario NSR, Luigi NSR and Samus' Gunship for the Nintendo Switch Version). Bodies record the number of matches won while equipped.