People on their phones while driving. Aside from the danger it poses, I have been stuck at a light behind someone who is obviously scrolling on their phone and then doesn’t realize the light has turned green. Sometime this lasts for 10-20 seconds, which is a lifetime when trying to efficiently move through a series of stop lights. I’m not an aggressive horn honker, and I feel like an asshole if I have to use it. But if you are fucking with the flow of traffic you deserve it.