A-Line shaping where the bottom is wider than the bust in a gradual way.
A Straight sweater where the width is equal all the way down.
An Hourglass sweater with waist shaping.
A Modified A-line which accomodates the hips.
Have I missed any? I have every one of these shapes in my wardrobe, as you probably do too. My favourite to knit is the Modified A-line where I make the hip about 3" wider than the bust, because I need to if I want to button it up. But I do love the A-line shape so the striped cardigan I'm knitting is going to be that shape.