Ice
The best ice for making cocktails with is crystal clear. This is achieved by high-end ice makers that gently freeze constantly running (and usually highly filtered) water. Not the sort of thing you'll find in the common household refrigerator. Standard ice contains trapped air as well as minerals, which causes it to cloud up, and as long as you use good quality water, and don't have things in your freezer that can impart a flavor to the ice, foggy ice is just as good as clear, except in presentation.