Hot cocktails are a hot trend. Not "hot" as in warm, but "hot" as in spicy, fiery, peppery. Bartenders are increasing their use of spice in drinks, giving us more than sweet, fruity, dry, and tangy to enjoy. There is something captivating about a hot pepper garnish, or a cocktail with an unknown heat that has been hidden by an infusion that draws us in.
Not all of the spicy cocktails are going to be in the red hot range of the Scoville scale, in fact drinks should be no where close to it. There should be a balance between the spice and the other ingredients of the drink and many of the drinks that I've included in Spicy Cocktails: Some Like It Hot and Fiery use a touch of black or cayenne pepper for a little zing. Others, however, go all out and include cut jalapenos or whole habaneros, and then some will go the route of an infusion, which is one of my preferred preparations. There really is a spice for everyone.
These are some of my favorite drinks because there is so much to taste, even within a single sip you can go from sweet to spicy to blow your socks off fire and back to a soothing sour. They are an adventure and great for the adventurous imbiber.
If you want to explore spicy cocktails further I encourage you to check out Kara Newman's book Spice & Ice, which is dedicated to this particular topic and is full of fantastic ideas for adding spice to cocktails. This Fall Spice Cordial is just one example, she has more on her website - Spice & Ice, and more... - and both links have more info about the book.