Tierney and Brown are the obvious answers I think; but for me, CalMac (The Ferryman) epitomises what it is to be Celtic; he never had an easy journey through the ranks and has been written off by many more than a few times.
He hasn't had the opportunity to play in one position and make it his. He's played in several different roles over the past 2 seasons and been superb in all of them - not an easy thing to do. It's as simple as the fact that to lay for Celtic he will take a shirt, any shirt, as long as it gets him in the team!
"he's like me and you, he loves Celtic too."
KTF