Mine is Koe no Katachi (A Silent Voice)
It is my favorite because of the beautiful story that shows the life of a bully and how hard to worked to get forgiveness.
He turned into a loner after being a bully and thinking everyone would stand by him which he was sorelymistaken. The stuff in this anime is really happening so it only adds to the feelings and emotions you feel when watching it.
The art style is amazing and the soundtrack as well even though it's only a couple of notes on a piano for most of it. It adds to the tension and feelings you're going through at different points in the anime. I think that music plays a huge part of anime and there is a right time for there to be music and a wrong time and I think that this anime pulls it off really well.