The AD&D Dungeon Masters Guide rather famously included a list of inspirational reading for the game, called Appendix N. In recent years it's become fairly common to see people make "Appendix N" lists for their campaigns, often branching out beyond prose media into films, comics, TV series, etc. that are supposed to give insight into the game's setting and mood.
Rifts is a difficult property for which to create such a list, partially because the feel of the game can vary so radically depending on the region of the world in which one's campaign is set, not to mention which elements are emphasized and which are downplayed. I've said this before, and it might sound a little trite, but Rifts is very much what you make it. One could say that about almost any long-running RPG -- Dungeons & Dragons is a blend of practically every conceivable flavor of fantasy at this point, for example -- but as a huge conglomeration of assorted science fiction and fantasy concepts that explicitly encourages the importation of elements from other popular genres, Rifts is particularly mutable. To put it another way, if you're using all of the books, Rifts is like dumping an appetizer sampler, a plastic jack-o-lantern full of Halloween candy, and a pu-pu platter into D&D's Chex mix.
With that having been said, the Rifts campaign in which I participated for years as a teenager had a distinct feel of its own. It was set primarily in the game's original backdrop, North America, which at that point was very much a "points of light" setting. Magic was largely downplayed, even though there were several spellcasting characters (one of which was my longest-running PC). The focus was on high-tech, post-apocalyptic action and heroism. As I've mentioned before, our characters were essentially soldiers of fortune that wandered a dangerous world, tackling powerful foes for money; initially similar to the "runners" of Shadowrun or Cyberpunk 2020, but increasingly more like a giant superhero team or (even GI Joe) as the campaign went on.
Though I've recently begun to reapproach Rifts as an adult, the fact remains that for most of my experience with the world, I and my friends were adolescents in the 1990s playing a game that was arguably targeted directly at us. The media that makes me say "that's Rifts" is almost always a product of that era. So, unlike Gygax's list, the "Appendix N" for my take on Rifts doesn't include much prose fiction (something in which I still don't partake much, considering my background in English and librarianship). It's mostly comics and animation, particularly the Japanese stuff that had so captured my imagination twenty-plus years ago, when playing Rifts was my favorite pastime. For me, at least, Rifts was basically an "anime RPG" before that came to mean something very un-Rifts-like in style, and that interpretation still colors the way I envision it.
Comics and Manga
Claremont, Chris. Uncanny X-Men series, particularly the Asgardian Wars paperback.
Kishiro, Yukito. Battle Angel Alita.
Macan, Darko. Grendel Tales: Devils and Deaths.
Otomo, Katsuhiro. Akira.
Shirow, Masamune. Appleseed; Orion; et al.
Takada, Yuzo. 3X3 Eyes.
Warren, Adam. Dirty Pair series.
Film & TV
ARTMIC Studio. Genesis Climber MOSPEADA; Genesis Survivor Gaiarth; Metal Skin Panic MADOX-01; Riding Bean; Bubblegum Crisis; M.A.S.K.; et al.
Kawajiri, Yoshiaki. Vampire Hunter D: Bloodlust; Cyber City Oedo 808; et al.
Kitakubo, Hiroyuki. Black Magic M-66; A Tale of Two Robots.
Oshii, Mamoru. Patlabor series; et al.
Gearbox Studios. Borderlands; Borderlands 2.
There are tons of things I've forgotten to include. I should probably come back and add to this as I think of them. (See the comments below for some excellent suggestions for additional material.)