Theres always some number of powerful non-creature spells getting thrown around at Commander tables, and being able to shut those down with only two mana is like having a safety net underneath you during the mid-to-late game when its not difficult to leave that mana unspent
It was pretty long, so I just focused on the parts related to setup and basic turn mechanics
Julius Jumblemorph Ixalan Vona, Butcher of Magan, Tishana, Voice of Thunder, Admiral Beckett Brass, Gishath, Suns Avatar Commander 2017 Nazahn, Revered Bladesmith, Inalla, Archmage Ritualist, Mirri, Weatherlight Duelist, O-Kagachi, Vengeful Kami, Mairsil, the Pretender, Taigam, Ojutai Master Razaketh, the Foulblooded, Zur, the Enchanter (Mummys Curse), Djeru, With Eyes Open, The Locust God, Karona, False God (All the Deserts), Nicol Bolas, Neheb, the Eternal Amonkhet Oketra the True, Temmet, Vizier of Naktamun, Atogatog (Cartouches & Trials), Hapatra, Vizier of Poisons, Samut, Voice of Dissent, Rhonas the Indomitable, Hazoret the Fervent Kaladesh Block Yahenni, Undying Partisan, Nicol Bolas, Child of Alara (Five-Color Energy), Rishkar, Peema Renegade, Kari Zev, Skyship Raider, Sram, Senior Edificer Commander 2016 Breya, Etherium Shaper, Atraxa, Praetors Voice, Tymna the Weaver // Ravos, Soultender Other Commander Decks Thada Adel, Acquisitor, The Ultimate Golgari Deck, Anafenza, the Foremost (shutting down shenanigans), Momir Vig, Simic Visionary (no green creatures), Kytheon, Hero of Akros (Tribal Gideon), Tasigur, the Golden Fang
All that being said, Gideon Blackblade doesnt really fit in competitively
