Going to Les Mis!
It blows everything else out of the water. It's just incredible. I would even dare to take musical haters to see it. It would soften your heart at least a little.
The second time I was in London, and friends and I had ventured to the West End one morning to see what shows had cheap tickets. We ended up buying tickets to Jerry Springer, the Opera, since that was about all that wouldn't break out budgets. A few hours later I was having dinner with a friend who had seen 'the opera' and mentioned that he probably should've walked out. I knew that if he didn't like, I'd probably hate it. What was plan B? Even though I couldn't get rid of my Springer ticket, I found a lone balcony seat for Les Mis that wasn't too terribly pricey and decided to see it alone. My friends ended up laughing through Springer, but I clearly made the better choice.
Third time's the charm tonight - I'm sure it will be fantastic.