Sweetened coffee makes me gag so no sugar or flavors in mine. I have a couple dark roasted blends (El Diablo from Intelligentsia & Peet's Major Dickason) that I like half & half in. I drink my s/o brews & espresso black.
Milk and sugar (it's too difficult to find cream over here). I've even put honey in coffee, which is nice provided you also like the flavor of that particular honey. I add flavored syrups if I'm making a latte.
No, seriously, I've even switched to no cream or sugar at restaurants too and enjoying it for whatever it's worth. That way, I can better judge the quality of the coffee. Heck, I even drank two cups of my grandma's coffee black... and it was harsh!