Tosca.

I've grown up with my dad cranking out opera at deafening levels, and continually telling me like its the first time every time, that the lead roles in Tosca are the pinacle of what opera singers aim for.  Thanks again to Frank, I'm particularily familiar with Cavaradossi's aria E lucevan le stelle, – “And the stars were shining".  It is a rather famous piece of music, but it moves me every time.  I teared up a bit hearing it last night, it was amazing.
This was the first time I've seen Tosca live and I loved it.  It was a rather controversial rendition of the Puccini classic - it's set in modern(ish) times.  Tosca wears sunglasses on her head and carries around a bottle of water in her handbag - perhaps not quite how it was intended.  Rather contreversially, the director has changed the ending - instead of killing herself at the end, Tosca is shot in the head at point blank range (After killing Scarpia, after he tried to rape her and lock up her lover - it's all a bit B&B isn't it - little wonder I like it).  I probably would have preferred to see a classic version of Tosca before seeing the modern version which the director describes as a "cross between Tarantino and Scorsese," but I still enjoyed it so much, and Jamie said he did too.