You want to find cards with a star on them, indicating that they are not commonly found
A my wife is taking ages in the shop game
Future Box utilizes a variety of attackers, but its most efficient attacker is Iron Leaves because of its ability to move energy on the board around to enable multiple copies of Iron Leaves to attack
(So yes, for those that like to dwell of the minutiae, technically permanents with landfall that change state do fall into the overall threshold category.) Let's look at another classic Magic card from days long ago: Is this a threshold card
Mox Opal was perfectly fine in Hardened Scales but was banned due to its interaction with Emry, Lurker of the Loch and Urza, Lord High Artificer
This card, Professor's Warning, would be beneficial in a black-based aggro deck looking to protect its key creatures or pump them up for a final push