I've placed a focus on haymakers that provide immediate or near-immediate value the moment they're cheated into play, so either combat damage (Demon of Loathing) or ETB (Lord of Change) or end step (Brainstealer Dragon)
Kaladesh, like most artifact sets before it, was pushed to the limit as far as power level was concerned, which led to multiple bannings in Standard (and was around the start of bannings being so in vogue in Standard)
Vampires are already one of Magic: The Gathering's most fearsome creature types, but what if you could turn your relatively fragile Vampires into bloodthirsty Demons
All in all, I expect [casthaven]Malfunction[/casthaven] to be a comparably bad-but-powerful removal spell much like Sleep Paralysis was
15 Magic: The Gathering cards per Set Boosterthe best MTG booster to open just for fun
You also have Skullcap Snail and Unscrupulous Agent to exile cards