As Soulwax once sang back in 1998, everybody wants to be the DJ. Everyone thinks their music taste is better than everyone else's, and few things will win you a "daggers" stare quicker than cutting someone's favourite track short at a house party.
The rather fab side effect of this wannabe culture is Djay, a virtual decks app for iPad. It provides you with two vinyl-style virtual wheels of steel, and a surprisingly comprehensive set of realistic tools to jump from one track to another. These include pitch shifting, beat matching, EQ and - of course - gain controls and a crossfader. If you're out for fun rather than a "pro" effect, you can indulge in scratching too, with intuitive swipes across the record surface.
It's so good that it's even used by some DJs good enough to get paid for the privilege, rather than just bedroom vinyl-scratchers. Recent updates have added new features like Airplay too, further increasing the usefulness of this app as a party host's dream tool.
Apps like this demonstrate what's so special about the App Store. It's a top-quality production for what would once have been considered a niche market.