I haven’t seen many plays. Maybe I’m not the best person to answer this question. I’m only 22 and memories of the Pittsburgh Steelers from say, the first ten years of my life tend to be fuzzy. I was a Steelers fan but I loved a lot of things. I watched DragonBall Z all the time. My Disturbed Ten Thousand Fists CD was a national treasure in my eyes. My judgement wasn’t very clear.
But to answer the question without being asked, the play I would take back if I could reverse the hands of time is Rodney Harrison’s 87 yard TD in the 2004 AFC Championship game.