I love Brave Song from Angel Beats~ Though I also love And I'm Home from Madoka Magica... Hard to pick a favorite...
I absolutely loved the ending theme for No Game No Life: Zero. The lyrics were just so much more meaningful and hit you right in the feels after having watched the movie. Spoiler: "THERE IS A REASON" by Konomi Suzuki
The best ending song of an anime I know is in this thread. https://forum.novelupdates.com/thre...-novels-to-complete-try-before-you-die.58634/
Not exactly the best per se, but the most memorable ones that stuck with me. Ranma 1/2 - Sweet Soul Revue - Pizzicato five (I can't remember if this is exactly the ending/opening though lol) Angel Beats - Ichiban no Takaramono