Basically all Auras have some synergy with the card, because you can play the aura early on to gain a temporary advantage for example play Paralyze on a Savannah Lions and then bounce them back to your hand, to play them again on something more relevant at a later stage of the game for example the same Paralyze but now on a Serendib Efreet
There are cards that might be houses in Limited or Standard that dont get a second look in the format
First, there's Sylvan Library
Card Name Mana Cost Type Sorcery Rarity Uncommon rules Text Search your library for a card, put that card into your hand, then shuffle
Notice how clean it looks, that is not an accident, that happens because I took the time to make sure all my pictures have the same lighting and backgrounds
Mechanics which affect the cost of other spells are also very popular, and often among the more powerful effects in the game