Love one another, as I have loved you.
Everything stems from this phrase. The sanctity of human life, Blessed Virgin Mary, your neighbour as yourself, Christ, God the Father, the Holy Spirit, and by extension, the Eucharist, baptism, confirmation, and all the ‘goodies’ of the Catholic Church.
There have been a lot of lists, but really they are just extensions of that one phrase, so if you want to be known as a Roman Catholic, it isn’t just about the Eucharist, Saints, etc., those are too ‘closed’ an example, i.e. one of many, where choosing one of them will negate the others, instead, just love one another, and everything else that has been said will be made relevant and apparent.