I love The Wire. Stunning characters, great integrity and observations in the writing, wonderful and subtle performances. But I think I'm the only one in my group who is (was) into it, so there wasn't that shared overlap with friends. And it's almost too good, too sophisticated, to aim for in an RPG! So in that sense we used Firefly more as a template - nowhere near as great as a show (in my opinion), but a viable template for 'troupe' type play and something everyone had seen.
The OP was particularly around formative influences as well - it's not comprehensive and there was a lot of stuff I was individually into - but I was trying to think about shared music, film, graphic novels - and the attitudes in them - that helped glue my groups together. For me the timescale was a time between, say, 1982 and 1992, although it's purely illustrative to get to the question.
Oh yeah, The Wire is more specifically a personal one for me more than for my group. Sadly, despite my urgings, only one of my regular players has watched it. It just popped into my mind as I’ve been considering this topic, and so I figured I’d mention it.
Also sadly, I left musical influences out of my initial list because I don’t think my group shares much there, certainly not as an influence to our gaming. I have my own, and I’d say they inform my games but perhaps less overtly than other influences.
I probably also left off cartoons of the era (or prior to it that we saw in reruns)that were influential to our group, and others mentioning them made me realize that. He-Man, Thundercats, Thundarr the Barbarian, GI Joe, Voltron, Robotech… those all certainly influenced each member of my play group.
In the Pirates of Dark Water, the alien world of Mer is being devoured by the Dark Water (or rather, the Dark Dweller). It was a pretty transparent narrative about pollution and global warming, but with high seas adventure.
I remember liking this as a kid and being sad that it was only around for (to my knowledge) one season. It seemed a bit heavier than most cartoons of that time.