I agree with Fullmetal Alchemist Brotherhood.
If anything the themes resonate more and more as I get older, and it's efficient with very little filler.
Kill La Kill is also fabulous to rewatch, similarly efficient and quick pace.
I really wish Ghost in the Shell held up better, but now that half that stuff is realistic it starts to feel more like a very human-rights violating cop drama. It was easier to have fun and ignore that when the universe they lived in was less real feeling.
Oh, I'd be a fool not to suggest Yuri on Ice, which is beautiful no matter how many times I watch it, and is also short and quick paced.
And super cute to use to introduce friends to anime.