Enchantment Auras affect specific cards and are therefore great to neutralize one of your opponent's more powerful creatures. Here are two examples from Return to Ravnica. I used Underworld Connections to enchant one of my lands and draw a card. You lose the ability of playing that land, but drawing a card can make a big difference for a black deck.
Here is a white Enchantment-Aura. This card can neutralize an opponent's creature.