I will be playing an entire League with the challenge deck, tweaking it a bit, and then playing another League right after
This sees a lot of play because it is versatile in which combos it works with but also because it is the most effective card in a few specific applications, the beating of red and green players being the primary one of these but also for other matchups where you need to dominate the board and immediately take all the tempo
There are so many cheap artifact spells that, even with only one turn to do it in, you could be quickly making a ton of Drone tokens
"The Stack and Its Tricks"
It pops up in Modern from time to time alongside Goryo's Vengeance, but its primary home is in Legacy, with decks like Sneak and Show and Reanimator abound
When you expect the game to be decided before you play all your cards like in many aggro decks and gambling with your worst card is worth it to try and upgrade your options