Idina Menzel in Wicked. When the lights went up at intermission (Saturday night just after opening) I turned to my friend and said "That was f#$%ing awesome!"
Bebe Neuwirth's entrance in Chicago. I was in high school and when she rose on that elevator I was floored.
The opening number of the original production of Ragtime. This reminds one of my top theatre moments. Glorious and, while I knew the abridged version of that number from the 1st recording, nothing could prepare me for that visual sweep.