#7 - Clan Defiance "I defy your Drana, your Ashling, & Sorin too!" Technically this one is Green/Red
If a Confusion card takes you by surprise, this gives you a great chance to try and counter it before becoming a game-winning threat
In exchange for exiling a land, players can gain extra mana from lands with the same name

So let's do that: Emrakul, the Aeons Torn +$0.225 Karn Liberated +$0.475 Kozilek, Butcher of Truth +$0.231 Ulamog, the Infinite Gyre +$0.168 Snapcaster Mage +$0.394 Temporal Manipulation +$0.406 Bitterblossom +$0.25 Demonic Tutor +$0.35 Goryo's Vengeance +$0.55 Liliana of the Veil +$0.51 Mikaeus, the Unhallowed +$0.175 Reanimate +$0.262 Tasigur, the Golden Fang +$0.02 Balefire Dragon +$0.08 Through the Breach +$0.538 Life from the Loam +$0.255 Noble Hierarch +$0.925 Tarmogoyf +$0.391 Vengevine +$0.225 Gaddock Teeg +$0.577 Leovold, Emissary of Trest +$0.13 Lord of Extinction +$0.09 Maelstrom Pulse +$0.246 Sigarda, Host of Herons +$0.05 Fulminator Mage +$0.112 Engineered Explosives +$1.02 Mana Vault +$0.125 Platinum Emperion +$0.088 Ancient Tomb +$0.45 Cavern of Souls +$0.435 Celestial Colonnade +$0.65 Creeping Tar Pit +$0.175 Dark Depths +$0.238 Karakas +$0.375 Lavaclaw Reaches +$0.03 Raging Ravine +$0.15 Stirring Wildwood +$0.01 Urborg, Tomb of Yawgmoth +$0.262 Total: $11.656 (These prices are based off of TCGPlayer Market, and will likely be out of date within an hour of my lookup

For some, they're an investment in the future, with ever-increasing card values having allowed a handful of collectors to make an absolute killing over the past few years
This is fantastic when the opponent has multiple cards in their hand or if they are close to winning