There was Accelerated Blue and the German Dragon in Standard, Suicide Brown and Iron Giant in Extended, good old Yawgmoth's Bargain in just about everything that allowed it, and then a lot of descendants of those initial Tinker decks that continued to get refined and grow in power until they took over Extended in New Orleans
During his Duel against Diva in the Pharaoh's tomb, Kaiba pulls "Obelisk the Tormentor" out of the ground and Summons it
Treasure tokens can be sacrificed to grant one mana
Any three color combination can work well depending on the precise mix of cards which show up for you
The original Counterspell was already a good card, but Mana Drain managed to be better, and that, combined with its sheer rarity, gives it a price tag of $362.22
When these events get busy (and the Final Fantasy prerelease definitely will be) being one of the people not trying to do everything on the spot will buy you so much more time to relax and appreciate the day