Was there a cool saint

By 'cool' I would assume that you mean a saint who the younger generation of today can emulate. I will give you a few examples of some modern saints or blesseds who lived typical lives when young but turned their lives over to Our Lord and died young.

Saint Gabriel of Our Lady of Sorrows (born Francesco Possenti) Was quite a wild teenager who loved dancing, partying, and chasing girls. He also smoked and loved hunting and target shooting, anything that had to do with firearms. After ignoring God's call several times he finally turned his life around and joined the Passionist Order and died young of tuberculosis.

Blessed Jose Luis Sanchez - Lived in a small town in western Mexico during the tumultuous Catholic persecutions of the 1920s. He was quite mischievous as a child but, at the age of 14, he joined the Cristero rebels who were fighting for religious freedom against the Mexican army. A few months later he was captured, tortured and shot by a firing squad.

Blessed Pier Giorgio Frassati - Came from an affluent Italian family who never lacked for anything. He was only a mediocre student but loved sports, especially mountain climbing and skiing. He used all his spending money to help the poor. He died suddenly of polio at the age of 25. It is thought he had contracted the disease from one of the people he was helping

Blessed Miguel Pro - As a youngster he was always in trouble with his parents. He loved practical jokes and sneaking cigarettes in his early teens. He became a Jesuit priest during the government persecutions of Catholics in Mexico. When most priests and bishops had fled Mexico for their own safety, he stayed and went underground to continue his ministry. Government police arrested him and he was shot by firing squad.

There are many, many more.