The Manhattan is one of the most classic cocktails and it's easy to see why. It's wonderfully complex, not too sweet, not too bitter, and wonderful to sip on.
I like to use a higher proof rye in my manhattans, such as Rittenhouse Rye. It's 100 proof (50% ABV) so it packs and extra punch into the cocktail and adds a nice spiciness to the drink.
My preferred vermouth for this drink is Carpano Antica. Carpano has some fantastic vanilla notes and really rounds out the drink without the aggressive herbal notes or bitterness present in some other sweet vermouths. I highly suggest experimenting with different vermouths and bourbons/ryes for this drink to find your preferred ingredients.