Six Shooter represents "isekai" in the most literal sense: gone is the average, whitebread guy with no personality transported to a vaguely medieval European fantasy world (which really needs to die mind you), now this story completely nails that alien feeling of putting the protagonist as a bonafide cowboy, with all of his wild west aesthetics and tropes, into a (still) vaguely medieval European fantasy world! (which still needs to die mind you xD)
All jokes aside, I would be telling a lie if I said I was attracted to this story immediately. Aside from that initial alien feeling of the cowboy protag, it doesn't really have anything special - the "OP cheat skill" this time is a gun, the whole starting town, starting people, adventurers guild, even the human/demihuman debates, you've likely seen them all at this point. But it's not until near the end of its first arc that Six Shooter really cements on what makes it stand out from the rest of the entries: yes, the world is completely average. But it is an average world with *a lot* of depth and thought put into it. The slime ecology remains one of my favorite details of this story, because it shows that the author has put in enough work to actually build a living, breathing world for our cast to live in and experience, despite being the same vaguely medieval European fantasy that everyone has been bored to death by.
And within the world, not only the creatures are alive, but so are the people. Six Shooter has, at least among the stories I've read and written reviews on, the best side cast there is. The welcoming townspeople of Floraison, the struggling but strong-willed resistance in Lillinberg, the royal twins Sol and Luna each with their own unique traits and worries, even the villainous, yet extremely "human" side of Slime Queen and Blut, everyone has come together to truly create a world that is worth seeing in every page.
Of course, it doesn't mean that the story has no weakness, and unfortunately in this case, our cowboy is the elephant in the room. Clint is, by no means, a "bad" character. However, his character writing works best if seen in a vaccuum. He's a real cowboy in every means - gruff, tough, shoots stuff, not talkative at all, and very distrustful of strangers. That's very good characterization... but it's not so good in the sense that it kills off his dynamics with the other characters. We still see moments of this - his talk with Marrie (and her daughter Merri at the end of the book) being some of the best moments in Clint's character imo, but other than that, it's just much more entertaining seeing the side cast work on their own while Clint is just... kinda there, doing his cowboy stuff (which most of the time is just watching, sometimes giving advice, and shooting stuff with his cheat gun).
Overall however, Six Shooter has a quality that far exceeds the rest of the bunch (that I have experienced). It's still missing that *tiny* bit extra to get a perfect rating (and I curse HF for not allowing .5 ratings xD), but make no mistake - this is pretty much the best 4-star review I've given.