While there are several that Im excited to play, Alchemists Talent jumps out to me as the most generically useful because Treasure is so powerful in Commander these days
Its also a little stronger than it looks because it exiles spells right from the stack instead of countering them
Divine Convocation is a Jeskai (blue/red/white) deck built around the mechanic convoke - with lots of big spells that can be paid for by tapping your little creatures
Lets say you have Krark, Sakashima cloning Krark, another Krark copy, and three Thumbs
Currently, Taeko, the Patient Avalanche seems like a decent addition to the 99 of Ninja Typal decks, but not much more
All three are also, in a rare twist, more than worth the usual $30 Secret Lair price point