This is really hard. There are so many opening that I love it's hard to pick one, but most of my fave OP are from Yorinuki Gintama-san
and Fairy Tail
As for favorite ending, it's
Sakuraon by Piko from Yorinuki Gintama-san.
The drawing in it is so beautiful, it kinda remind me of Okami
For OST it's from Fairy Tail, those music by Yasuharu Takanashi is very epic
My most favorite track in the album is
Invoke Magic