Other than on the right bank in Bordeaux in my opinion Merlot is a secondary blending grape. Though there are some upper end examples from Washington state that are quite good.
Sangiovese and Merlot are a rather nice combination in wines from Tuscany. The Merlot balances out the tartness of the Sangiovese. It also adds considerably more fruit to the nose.
Sangiovese based wines always work well with red sauces. They have enough acidity to compliment the tomatoes.
Speyside wrote: