Tom McCourt is a minor character in Cell.
He is one of the survivors of The Pulse along with Alice Maxwell and Clayton Riddell. McCourt, like millions of other people, owned a cell phone prior to the events caused by the Pulse. And, like plenty of others who managed to escape it, McCourt was saved by circumstance and not deliberate action.
Tom McCourt is a small, unimposing man who first comes to Clayton RIddell's attention when he shouts "Look out!" on the street Riddell is standing on, just as the chaos caused by the Pulse begins. Riddell flees to the Four Seasons hotel alongside Riddell, and assists in bringing Alice Maxwell inside, too. The three leave Boston that same night as the city burns to the ground, and go to McCourt's house in the nearby suburbs.
Once they are safely inside the house, McCourt explains that it was his cat that saved him from being yet another victim to the Pulse; a few days prior, the cat had knocked his cell phone off the kitchen counter with its paw, disabling the device. McCourt did not use his cell phone as often as many people, so he still had yet to get around to replacing it when the Pulse hit. The next morning, McCourt recognizes many of his neighbors among the roaming "Phoners", people whose minds were destroyed/taken over by the Pulse. Unable to stay at his home, and unable to take his cat with him, McCourt regretfully leaves the cat behind to go feral, setting out some food and thanking it for saving his life.
McCourt later wields a fearsome fully-automatic rifle he nicknames "Sir Speedy", implied to be a Kalashnikov-pattern rifle like an AK-47 or AKM, that was illegally owned (under Massachusetts state law) by one of his neighbors. McCourt had no prior firearms experience whatsoever, so the one notable time where he tried to use it, he holds down the trigger and the resulting muzzle climb means he essentially empties the magazine into the sky.
Eventually, McCourt joins other surviving "Normies" in heading north into (former) Canada, counting on the impending cold to kill off most or all of the surviving Phoners, who are both unable to care for themselves beyond basic foraging and disorganized and leaderless following the death of the Raggedy Man. He wishes Clayton Riddell well in his hope of locating Johnny Riddell, his son.
In the film adaptation he is portrayed by Samuel L. Jackson.