Now, I will admit that there are legitimate concerns about unbanning Splinter Twin, with perhaps the biggest being that having a combo-control deck at the top of the meta tends to drive some people a bit crazy (see: Alrund's Epiphany in Standard)
You can only use each effect of "Goblin Biker Mean Merciless" once per turn
All Hallow's Eve A black/red sorcery at $588 raw / $764 PSA 10 with 77 annual sales
The only thing that keeps it from being the best fire-type card in the game is a relatively low HP

Where to buy Korean Pokemon cards List of Korean Pokemon card extensions and decks: The following Pokemon extensions and battle decks were released before XY: Series 1 Start of an Adventure Torterra, Infernape, Empoleon, Raichu decks Series 2 The Burning Confrontation Series 3 Space-Time-Crash Dialga & Palkia decks Series 4 The Different Dimension Series 5 Mysterious Seven Series 6 Crescent Moon of Darkness Cresselia & Darkrai decks Series 7 Hidden Powers Series 8 Beautiful Legends Series 9 Miracle of the Lake Series 10 Guardians from Ancient Times B/W Series 1 Black / White collection B/W Series 2 Red Collection B/W Series 3 Hail Blizzard & Psycho Drive B/W Series 4 Dark Rush B/W Series 5 Dragon Collection B/W Series 6 Dragon Blast & Dragon Blade B/W Series 7 Cold Flare & Freeze Bolt B/W Series 8 Plasma Gale B/W Series 9 Thunder Knuckle & Spiral Force Shiny Collection EX Battle Boost XY 1 XY 2 Wild Blaze

It happens on both Gilgamesh entering or attacking, so you guarantee the effect goes off if Gilgamesh hits the battlefield at least once