In my attempt to rush out the post, I probably overgeneralized what a Gestalt was. I almost want to take back saying the One Ring of Lord of the Rings is Gestalt, at least in the sense that a ring is a ring, and by itself, is not very unique. We'd be getting closer to Gestalt if we could sum up what the ring does that makes it unique, such as "A ring which grants unlimited power to those powerful enough to wield it" (or something). In your first idea, the Gestalt is most definitely the vine coming from the eye. It was the first visual you described, and it is most certainly vivid and unique. You say someone has a vine growing out of their right eye and everyone can imagine it, and I, for one, can think of no other example of that image. Think of the Gestalt as something visual (though not necessarily a noun), which can be fairly summarized in a sentence or less. The vine in the eye was perfect. What can you say for the other three examples that can have such an instant impact as the vine-eye? As for characters being Gestalts themselves, it's certainly possible. If they're visually unique in some fashion, as to be instantly recognizable, then they certainly can be. The Gestalt of practically any superhero comic is the superhero, since their costumes are outlandish and spectacular. The Gestalt character of the original Star Wars trilogy is probably Darth Vader: his design was meant to be akin to a futuristic Samurai outfit, which is something not seen elsewhere. Do any of your characters from those last worlds have at least one unique feature about them, such that if you drew them, a viewer would be interested to know more about them?
I see what you mean. Perhaps it was me trying to grasp the concept. On the sidenote, I admire your capitalization of "Gestalt", the word being a German noun which, using the rules of the originating language, ought to be capitalized. Does it have to be visual, though? Is Agent Coulson a Gestalt, being the first person in MCU to be ressurected? Pronounce "Tahiti" somewhere around his name in the sentence, and people recognize the character in a moment. How about the Machine from Person of Interest? It's the first friendly and, dare I say, caring AI of such scale in the mainstream media. You can barely draw it - only its interface - but those faintly familiar with the series would probably recognize the... khm, character, as well. How about Chuck Bartowski, for the Intersect? Captain America, for the serum in his veins (shield seems to be in the same category as the ring, even though it's outlandish in the modern era and quite powerful on its own)?
I didn't make up the concept of the Gestalt of a world myself, I read it in a book I no longer own, so my own memory of what it exactly means may be hazy. When I say "visual", what I mean is really "easily imaginable". A Gestalt works a bit like an advertisement: imagine someone has never before heard of your world. If you had a movie poster to show it off, or a tagline, or a one-sentence description, what is the unique and central feature of your world that would make a person say "tell me more"? I cannot speak to those example you just gave, since I don't know of most of them (the obvious exception being Captain America). I would hesitate on calling any of them Gestalts, since, by your descriptions, they do not seem unique enough to capture the interest, without already knowing something about the IP. But if you can describe or show them such that you explain a unique (and important) aspect of them that is intriguing, then they might be Gestalts. Like I said before, to simply say "The One Ring" would have been a bad example, since you'd have to already know what we're talking about to not assume LotR is a love story. To say "There is one ring which grants unlimited power to those who are powerful enough to wield it" can get much closer to a Gestalt, since we are now not only describing an item central to the world, but also describing what makes it unique from other rings in other worlds. Also, I capitalize Gestalt because I get weird about vocab words. I try not to, but I capitalize too much! :p