They have the rights to all your content
I.e., literally everything you've ever tweeted. Whether you use Twitter as a newsfeed or to share the boring minutiae of your life in 140 characters all the live-long day, Twitter's terms of service clearly states they retain the rights to everything, even if you close or deactivate your account.
You don't actually own any of the music you buy
As one of the wordiest user agreements out there, you better believe iTunes' Terms and Conditions is flush with sketchy stuff. One that particularly stands out is the fact that, despite how much money you've dropped on Taylor Swift and Rihanna remixes, you're paying for the right to watch or listen to that media... but you don't actually own any of it.
You can't use anything in the iTunes store to make biological weapons
So, you can't use apps to break the law. More specifically, you may not use them in the "development, design, manufacture, or production of nuclear, missile, or chemical or biological weapons." OK, sure!