tell me what, tell me what, tell me what you want, I don't know why, don't know why, don't know why you afraid, so put your glasses on, nothing will be wrong
And because the traditional Production I.G + Kenji Kawai self-indulgant "here's 1:30 of contemplative low-key music over near silence and cool art" sequence is one of my favorite things in anime:
Also pretty much anything by Yoko Kanno gets a thumbs up from me. Absolutely love the GitS SAC and Cowboy Bebop OSTs.
I try to keep track of some of my favorite anime songs on YouTube, but like half of them get removed/deleted/copyright takedowns.
Is there any reasonable way to do this outside of piracy?
I have some stuff ripped from CD, but can't do that for everything (not going to buy a cd for every stray track)... Guessing no Amazon MP3 equivalent out there for anime.
Most have been mentioned here but this is turning into an OP lovefest when in reality OST are unsung heroes in anime.
You can set themes and moods on just OST alone. Big props to JoJo, Land of the Lusterous and Made in the Abyss for their excellent use of soundtrack. Especially Battle Tendency (Part 2 of JoJo) for its bombastic numbers.