With a billion users, no surprises here: Facebook is the top mobile application for each age group, ranging from a low of 14.8% of time spent with mobile apps among 18-24-year-olds to a high of 18.5% share among 25-34-year-olds. The analysis of mobile app consumption in June also finds that Pandora Radio is a top-3 app among each age group, while YouTube is among each bracket’s top 5. Twitter only ranks among the top 10 for the 18-24 group, and trails Snapchat among that demographic.

Checkout ComScore's Mobile App report, definitely worth a read:  Download here