*checks her anime list*
Apparently the only things I've given a 10/10 are 5 Centimetres Per Second and The Place Promised in Our Early Days. Thinking back on them, I don't think I'd give them a perfect score anymore. They're beautiful and the music and art direction still amazes me every time, but the pacing is pretty off in both of them and considering I can't really remember the plot all that well of the latter, it probably didn't leave that great an impact on me.
I'm very stingy with perfect scores, though. Even my favourites of any kind of media never get 10/10 because there's always room for improvement in something. I don't feel like I can actually give a perfect score to something so I typically don't.
However, having just recently rewatched the whole series, I think I can safely say that Cardcaptor Sakura is the closest I'd probably ever get to giving something a 10. I loved everything about that anime and watching it all the way through with a close friend who appreciated it just as much as I did made it so much better. The animation didn't age all that much (it still looked great in a lot of places and even the mediocre animation looked fine), the music was still great, the acting was fitting and just... everything still felt so magical. Nostalgia crossed with what was always an excellent show makes it as close to a 10 as I could probably justify. :P