Selfies period. I know it's just a fun little thing that people have grown accustomed to doing without probably putting much thought into it, but it makes people look more self-absorbed and narcissistic than usual when they're so obsessed with taking pictures of themselves at random intervals during the day. Whether they're in front of a mirror, in their car, in the bathroom, in bed, on the computer, people seem to love snapping photos of themselves, sometimes even when they're naked.
I'll also be glad when a lot of folks realize that using the word "hipster" as an insult anytime a person holds opinions that go against the grain makes them look stupid, especially considering that from an historical point of view, the majority of people who have ever lived period have been wrong about the things they knew (or thought they knew) and believed to be true.