Now that I think of it, I tend to cheat a lot when I write these Top 10 cards articles, but I hope you can forgive me because I have selected an entire archetype for the last spot of the list
Illustrated by Craig J Spearing Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Legal Brawl Not Legal Legacy Legal Comp
A 5/5 Elemental with Flying, its base mana cost of (7)(U)(U) is deceptive thanks to its cost-reduction mechanic: the spell costs (X) less to cast, where (X) is the greatest mana value among Elementals you control
At time of writing, theres only one NM listing on the entire marketplace, for $399.95
Duress I card I associate both with old school formats like extended but also a card suitably balanced that it has seen countless reprints making it modern playable and periodically a standard card too
For a six-mana investment, they can turn a creature into a killing machine