I tend to use heavy whipping cream, when I use any at all. Negligible carbs in the small amount I use (it goes a lot further than half and half or milk). Some people don't like how much calories are there.
If you aren't worried about the calories and want an interesting experience, you can try the "bulletproof coffee recipe"
Large cup of coffee
2 tablespoons grass-fed butter
2 tablespoons coconut oil
Blend it with a hand blender til foamy and creamy.
It has about 443 calories, but if you're like me and can't seem to eat enough to maintain weight, it's not a bad way to start the morning!