1.
Paint it Black - Lee - One of the defining moments in the series; an extremely difficult, iconic song brought to life by a gifted young performer. The shot of JB watching with his mouth hanging open says it all.
2.
Don't Rain on My Parade - Craig, Daniel, Lee - a SHOWTUNE! OMG!

Brilliant performance from all three men. Three different personalities and approaches melded together into three minutes of magic. I'm gutted that Daniel and Craig are both gone now.
3.
Mack the Knife - Lee - Great song from one of my favorite musicals of all time, so maybe that factors in to it. Nah.

It's a polished, thoughtful performance full of both energy and cynicism. Gives my Jerry Orbach recording a run for its money. And that's saying a LOT.
Most astonishing event of the series would be Craig singing
This is the Moment. Up until THAT moment I'd failed to see what Bill Kenwright was going on about, but as Craig sang and acted the song I realized that it's BILL who is the true teacher on the show, and that his instincts weren't wrong. I ate my words and became a fan of Craig - something I would not have predicted six weeks earlier. The combination of great teaching and a hard-working student provided sheer magic.