Negroni
I also love the Boulevardier, a version of the Negroni using Bourbon instead of Gin. The sweetness of Bourbon plays with the bitterness of Campari in a different way... The negroni is more about the botanicals and citrus of gin. Both are amazing drinks and I can't say which one I prefer, but they are different enough that if you like one, you might like the other even more.