Besides all that have mentioned above, I feel it is The Holy Eucharist:
Many Christian faiths outside the Catholic Church do not believe inthe presence of Jesus in the Eucharist. The reply of the Catholic Churchis this: Mathew 26:26 - 28
And whilst they were at supper, Jesus took bread, and blessed, and broke;and gave to His disciples, and said: "Take ye and eat. THIS IS MY BODY"And taking the chalice, He gave thanks, and gave to them, saying; " Drinkye all of this." "For this IS MY BLOOD of the New Testament, which shallbe shed for many unto remission of sins"
This is the New Covenant laid down by Jesus, whose Flesh is truly presenton the alter VEILED as the consecrated bread, so that those who are calledmay not die but have everlasting life. The Catholic Church and has beenfor 2000 years doing this in memory of Jesus as he said do this in memoryof Jesus as He had said; "DO THIS IN MEMORY OF ME." This Command laid downby Christ is the reason for the existence of the Mass. Through there aremany man made and modern Bibles in our society today, they all have onething in common and that is Jesus Said " Take and eat, THIS IS MY BODY".The Jehovah Witness Bible is the only Bible that states otherwise; "Takeand eat, this means my Body." By this erroneous tampering with the Bible,they have diabolically taken away the Knowledge of HIS DIVINE PRESENCE.
The consecrated Eucharist is more than just a meal, it is a SACRAFICIALMEAL, and is the sacramental RENEWAL of the Cross of Calvary, in that thevery same Flesh of our Lord Jesus Christ, sacrificed on the Cross 2000years ago, is made present again on the Altar today during every Mass.The Host becomes the actual body of the Crucified Lord - JESUS IS PRESENT,BODY , BLOOD , SOUL AND DIVINITY. " THIS IS MY BODY." Further referenceindicating that Jesus is present in the Eucharist (MK 14:22, LK 22:19,JN 6:35, 1COR 11:27). In the Holy Bible Jesus States: John 6:51
"I am the living bread which came down from Heaven. If any man eat ofthis bread, he shall live forever; And the bread that I will give, IS MYFLESH, for the life of the world." Jesus is not speaking in parables noris he speaking symbolic, Jesus is saying literally that " … The bread thatI will give IS MY FLESH." If we do not receive the body of Christ we haveno salvation within us; Jesus has thus laid down His law for salvation.
Some people are often scandalized on this point as they find it difficultto believe that Christ would actually give us his body to eat and drink.However, our lord answered those Pharisees in his own time, that did notbelieve he could do such a thing by saying to them ".... Whoever eats myflesh and drinks my blood has eternal life, and I will raise him on thelast day." (Jn. 6:58,54), So it seems that these arguments are nothingnew, it scandalized the apostles and the Pharisees but our lord simplyput it to the apostles "shall you to abandon me" it is only human to placelimitation on the power of god, however that is because we place our thinkingon earthly levels as we forget that with God all things are possible (Matt19:26).