Pierce.
I grew up watching the Celtics with my dad, but didn't really become a real fan, as in "I like this team because I like them, not because my dad roots for them.", until Pierce's rookie season. I was 14 years old, saw highlights of Pierce's first regular season game versus Toronto & just liked the way he played, started to watch games on a regular basis, & grew to develop my own affinity towards the team. Have been a faithful follower ever since.