There are a few exceptions (and more than normal for Masters 25 , which has a very strong suite of uncommons), and these are listed along with my pricing in the appropriate sections
The Frightful Four If youre tired of blue players wrecking your day with countermagic, consider using The Frightful Four to punish them
Festival sticks around permanently, however, with the trade-off that your spells damage you when you cast them
Both seem like they're designed as MTG commanders, but while Rakdos is doing his Standard sacrifice shenanigans, Aurelia gets you bonuses when everyone swings with a bunch of creatures
Mount & saddle is a gameplay mechanic being introduced in Outlaws of Thunder Junction that allows players to tap any number of owned creatures that have a certain ability in order to saddle them together, thereby ensuring that anything that affects one, affects all of them
This one can counter anything, so long as your opponents cant pay the one mana, making it one of the better counterspells in the color