gundam thunderbolt - theres two ovas of 4 20-25 minute episodes each or there's two films - there's no real good guys in this one both sides of the conflict have some right bastards but theres also some tragic figures where you're like "damn life screwed you hard"

planetes - one of the most scientifically accurate sci-fi series out there its slice of life so its not all pulse-pounding action weightless scenes are done at a higher than normal (for anime) framerate to increase the smoothness and JAXA gave advice during production

.hack//sign - warning: very slow it takes place in a video game called "the world" and your main character is trapped in it kinda like sword art online but this was before SOA (actually technically the SOA books came before with the first book being 2001 and this being a 2002 series) but despite that theres very little action and it's more about the mystery of the world