In the past when I've asked what saints people are most interested learning about, St. Francis of Assisi (1181/1182-1226) has been the name that was brought up the most.
St. Francis is mostly known for his love of animals and nature, and the legends that popped up about him with animals. That is why his feast day in October is commonly celebrated with Blessing of the Animals services.
Francis is also known for bearing the stigmata, the marks of the nails in his hands in feet that Jesus bore from the Cross. Francis received these marks in prayer, but told only few about them and hid them with bandages during his life.
What was really important to Francis was the poor, and that is the crux of his story. Francis grew up the son of a rich man, and he lived an extravagant life. As he grew older, though, he found he had a heart for the poor around him, which led to his sense of call to serve the church.
Where before he squandered the wealth his father gave him, now he used it to help the poor. This made his father furious, and he threatened to disown him. Francis gave his father back even the clothes on his back so that he couldn't say Francis had taken anything away from him. Francis then gave his life to serving God in poverty, forming the Franciscan Order of Monks, and inspiring St. Claire to form her own order as well.
The lesson we can gain from Francis is showing God's love to those who truly need it: the ones who have nothing. He chose to live in solidarity with the poor, just as God showed solidarity by living with us through His Son Jesus Christ.
One final note as we approach Advent, and Christmas shortly after: Francis constructed the first crib used to create the Nativity Scene.