If only to go against expectations, I realized that the roll I call for most often that ISN'T the d20... is the d12 (for random encounters), followed by the d100 (for everything else). So I voted d100. I figured d12 would be up there , partially cuz of the thread title, and partially because yes it is a great die.
When I'm not sure what kind of roll to call for for something random, I call for a d100- because I can easily make it fit any table I then pull up.