Yoshimaru, Ever Faithful + Reyhan, Last of the Abzan Any deck with Yoshimaru, Ever Faithful in the command zone looks to be aggressive
Shock is a very strong effect, just because we have Lightning Bolt and multiple other slightly better than Shock cards doesn't mean Shock is itself bad
By reducing your own spell costs while you tax opponents, it forces the game to slow down on your terms and makes it extremely difficult for other decks to resolve key spells efficiently
Its also worth mentioning that this doesnt just happen during your turn, but each turn, so if you have anything that allows you to cast spells from exile on your opponents turns this would trigger then as well
In De la Ville, Valrie-Ins
Other permanents can have subtypes that define mechanics of the cards