DJ Player Free (iOS)
Of the many DJ apps available, this one seems to be the most serious. The interface is not like a turn table as in many of these apps, so you will take some time to get the hang of this interface. However, the app has everything you will need to mix your own brand of music. You can tweak Deck A and B separately as well as mix the songs to your requirement. However, we missed a record/save feature.