Gun Dragon is a series of DARK Machine monsters. This series focuses heavily upon the usage of coin tossing to activate their effects to destroy your opponent's cards on the field. The original "Gun Dragon" monsters are ones that need to Tribute Summon (although "Gatling Dragon" can only be Fusion Summoned whilst "Twin-Barrel Dragon" is the only monster in the series that can be Normal Summoned without a Tribute). The appearance of this series seem to be based on firearms (although the TCG censored the fire weapons changing it to lasers) and share "dragon" in their name though they aren't of the Type (this is can also be seen with the Cyber Dragon cards).