Duel Monsters
The phenomenon of decks that only have one copy is a bizarre side effect of a world where color is so cheap that you can play this, Wrath of God, Cloudthresher, Jund Charm, and Rhox War Monk without even worrying that this might be pushing it
Skeledirge Ex Common Threats Skeledirge Ex has two main problems
Most of the things you've seen during the latest stages of the Sword and Shield era are still with us, but older cards like the whole Shady Dealings engine, the Quick Ball, the Scoop Up Net, and the Evolution Incense are now out of the rotation, which means that every deck has to change its strategy and resources

Decklist: Affinity in Pauper Chromatic Star | Illustration by Alex Horley-Orlandelli Creatures (8) Gurmag Angler Gearseeker Serpent Kenku Artificer x2 Myr Enforcer x4 Instants (16) Reckoner's Bargain x4 Metallic Rebuke x4 Galvanic Blast x4 Deadly Dispute x4 Sorceries (4) Thoughtcast x4 Enchantment (1) Artifacts (11) Blood Fountain x3 Ichor Wellspring x4 Chromatic Star x4 Lands (20) Swamp Island Great Furnace Darksteel Citadel Vault of Whispers x2 Seat of the Synod x2 Drossforge Bridge x4 Mistvault Bridge x4 Silverbluff Bridge x4 Sideboard (15) Nihil Spellbomb Makeshift Munitions Unexpected Fangs x2 Krark-Clan Shaman x2 Devour Flesh x2 Red Elemental Blast x3 Blue Elemental Blast x4 I could post a Modern or Legacy decklist here, but affinity is the king of the Pauper format