I have a couple of secret weapons that I find myself using surprisingly often.

First is Mesh Transformation... This should be called the tweaking tool. It's great for fine tuning a drawing (sometimes even for major overhauls.) Is a character's muscle, or head, or cheek not quite as round or straight as you would like it? Tweak. Is one eye slightly off compared to the other? Tweak. Or maybe you need something to be just a bit longer or shorter than how you drew it so that the perspective or forced perspective looks right. Tweak.

Another one for me is Stream... I use Stream all the time to create cross hatching or shading textures. It takes a bit of practice to get used to all the options, but Stream creates it's own layer (sort of like a correction layer) so you can always go back and tweak the control points if you end up changing your drawing.