Just got brain freeze, any help for a deck ?

@Tristan775 I like making "shrink" decks with Beastly Heroes (such as Brain Freeze). This mainly consists of using -1/-1 effects (Zombies and Tricks) that weaken plants. I also like to play big cards such as the Nurse Gargantuar (like you suggested) in the later game as the win condition. Depending on the Beastly Hero, I also like to use other effects that are related to its other class. For Brain Freeze, you could try adding some deadly effects as an effective way to destroy plants that are way too large to shrink down.