I confess, I had to click this morning's Google logo to figure out what the heck it was. Jumping frogs # Rossini's birthday, because I didn't notice that one of them was a barber. He's not wearing 18th c. Spanish clothing, either.
That said, yes, it's Giacchino Rossini's birthday, and all the best people are celebrating. As Joshua notes, his greatest achievement was his last opera, Guillaume Tell. I nearly fell over the only time I've seen it performed. It's a towering masterpiece of great musical and theatrical depth, with a most remarkable finale.
I'll get to that in a minute. Let's start with the overture. Yes, you might think you know it, but I was flabbergasted to find recently that a highly knowledgable musician friend had never heard the whole thing. There is no greater opera overture, from the solo cellos in the first section to the call to arms in the last.
Here is a great, great performance of the duet "Ah, Mathilde," in the wrong language, but never mind. Marcel Journet as William Tell and Giovanni Martinelli at his youthful and heroic best as Arnold:
Here's the finale, all prayers and flowing harps. This is after quite a lot of tense action. The performance embedded below is not quite the most professional imaginable, but it'll give you an idea. If you want to hear more, you could pick up the recent recording conducting by Antonio Pappano or the older recording (in Italian, alas) with Pav and Caballe.
If you ever have a chance to see Tell, buy a ticket immediately. You won't regret it for a second.