Long thin oblongs are often known as baguettes. Tapered baguettes also exist. This is done largely to protect the stone, as any sharp points are vulnerable to getting chipped. Most oval diamonds are like a squashed round brilliant. Marquise Marquise or navette shape is like a long oval which has been stretched out to a point at each end.
Similar comments apply as to the oval.
Triangle Not a popular shape. It is normally a variation of the square cut, in that its facets are step cut, but some triangle shapes are a modification of the round brilliant cut. Pear One half oval, and the other half marquise. Heart Pear shape with a notch cut into the top. Princess A relatively new shape, oblong, usually square or almost square, but with a modified brilliant cut arrangement of facets instead of a step cut.