Rocks or neat?
Rocks. Fewer, larger cubes is the way to go. Or a single ice sphere. You’ll get the chilling effect without dilution.
Cocktails or straight?
That depends on the whiskey. If I’m drinking Gentleman Jack, I like a cocktail. If I’m drinking something more like a Single Barrel or a Sinatra blend, I’ll go straight. I do what the whiskey tells me.
So what’s a good whiskey for cocktails?
In the Jack Daniel’s range, I call Gentleman Jack our “cocktail whiskey,” because it’s gone through mellowing a second time. Your classic whiskey cocktails contain some form of bitters, so if your whiskey has a lot of oak, it’ll compete with that (because they hit the same tastebuds on your tongue). Gentleman Jack lets you keep the bitters light, but keep them prevalent. All of the worst whiskey cocktails I’ve had have the same thing in common: people had overdone the bitters in them.