Snapchat - but more on principle because I like to read back over conversations and see old pics and Snapchat is designed to be the opposite of that. Not in my interest in any way.

Battle Royale games - Not interested.

It's actually weird that I can't think of much here because I always feel like I'm an old git who doesn't get the new fandangled stuff, but I guess maybe I'm okay after all. But then it's entirely possible that I'm simply not clued in on what is hip with the kids these days... maybe there's some other app that's picking up steam.