There are about 5000 recognized saint, blessed, venerable and holy angels in heaven. We know from the Scriptures that they actually are by the millions upon millions. All the saints, and angels hear all the prayers. This is why "calling the Lord's name in vain" is a Commandment against.
Unknown saints may intercede for a particular prayer by means of a Saint who is known to us. For example invoking the intercession of Saint Maurice & Companions will bring a minimum of 6000 Saints, because Maurice was a Roman general ahead of 6000 Roman soldiers who were all martyred for the faith. The intercession of St. Maurice & Companions logically might be useful during war, since this complete army knows what it takes to win a battle. To invoke a Saint such as the Little Flower might bring many thousands upon thousands of little souls who love God to their utmost.
Some saints offered marvelous poetries to Our Lord, such as Saint Gertrude the Great, or to Our Blessed Mother, such as did Saint Francis of Assisi.
All the invoked saints in heaven have a fair shot to at least ask for the intercession of Our Blessed Mother, who is always ready to assist us towards Her Son. This is how it seems to work in heaven. Naturally our own intentions must be loving, charitable and faithful.
There are some saints who are never called for. Those have been forgotten and are waiting. For example Saint Philomena was forgotten for over a thousand years until been recently discovered. This little Greek princess, martyred for her love for Jesus, seems now to be making-up for the long years of silence from earth. She is known to be a real darling for her many intercessions that range from the big to the cute. Long-forgotten Saint Philomena, powerful with God, proves that saints, blessed, venerable, as well as the holy angels are longing to help us.
So in this forum, please tell us who is your favorite Saint, and please tell why?