Well, besides being able to remove opponents shields and weapons, for virtually no cost (eg wings + airbourne creatures), you could play an air/ death deck passing boneyards to the opponent and killing a huge amount of skeletons with thunderstorm to increase bonewalls or gain a huge amount of quanta with soul catchers or a similar idea with rain of fire. You could pass a fire shield + voodoo dolls, or pass a permafrost shield to keep freezing your creatures for use with catapult perhaps. Duplication of unstable gas with steal could work well. I'm aware some of these might take a bit of work to become practical, but I reckon there are some strong potential uses I haven't thought of.