A bottle with a square bottom and round top.

I modeled it starting with a sphere and a cube. I used the deform tool to make an egg from the sphere and then Boolean subtracted the cube from the egg. Sweeps and point editing finished the control mesh. Several levels of subdivision surfacing smoothed it and the shell tool made it hollow after extracting the final surface. The geometry around the neck needs some work. The stopper is a cylinder rounded and tapered.

Software: trueSpace 7.6 model side.