Sweetened condensed milk!
1-2 cups of chilled strong coffee
4-6 tbsp of sweetened condensed milk
Mix these together in a nice glass (if it's a clear one you can try and make designs) and add ice cubes. Whatever happens, don't skimp on the condensed milk, or it will just be disgusting. Add until your coffee is a pleasing, creamy caramel shade, which is the best indicator for the proper amount of condensed milk. And don't be ashamed to, like Winnie-the-Pooh, taste the condensed milk liberally to make sure it hasn't gone bad while you're mixing the coffee. ;-)
If possible, make some unsweetened coffee ice cubes. But if, like me, you've somehow managed to lose your circa-1990 ice cube trays, and have subsequently decided you don't want any other trays in the world, you can use regular ice--it will just dilute the coffee as it melts. Most people don't care, but this deeply disturbs me.
Also, I find that drinking iced coffee with a straw makes it taste so much better.
"No coffee can be good in the mouth that does not first send a sweet offering of odor to the nostrils."
~Henry Ward Beecher