Flaming chalice is always my first answer. The funny thing is I don't actually own one, or even a symbol of one. It's kind of a problem because I don't go to church anymore which is where I always had them before. My brother got a beautiful silver chalice necklace at his Bridging ceremony (which acknowledges the passage of the adolescent from the youth church to the adult church) and I am so envious; I never Bridged.
The chalice is usually lit at the beginning of service while chalice-lighting words are said; for some churches they are the same every week or among churches, while for others they change depending on the rest of the program. In that way it signals the unity of the congregation (often the minister or other designated person will say words and the congregation will respond) and the conscious recognition of sacred space.
To me...I don't know. I like fire. It has always been a symbol of the haven of intellectual and spiritual discussion, learning, and companionship that the church was for me when I was growing up in it. It is really nice to be raised in a religion that you can affirm throughout childhood and adolescence and into adulthood (at least young adulthood so far). It also represents the simultaneous diversity and unity of our community, as there are so many representations of the chalice to be found in its position as community-wide symbol.
My next answer would be the ankh as a symbol of my newer religion. I do have two ankh necklaces, both of which came to me completely spontaneously, although one is broken right now and I need to remake it. I used to make ankhs out of
gimp. Still working out what it means to me. In my tradition it is a symbol of life and by extension ma'at, although the feather is also used to mean ma'at. Many images of Kemetic gods feature an ankh carried in a hand. Of course it is more nuanced than "life," but that's as far as I have advanced in my understanding of it so far.