That's a hard one... I've acted in everything from Fiddler on the Roof to The Pirates of Penzance.
I would have to say that my current favourite is The Pirates of Penzance. Despite how much singing there is in that show (it's pretty much an opera). It's a really fun show
Funny story actually.. I lost my voice during the second weekend of that show. I was the Pirate King (one of the principles).. That was interesting.