Baculovirus infected insect cells.
Insect cells are a higher eukaryotic system than yeast and are able to carry out more complex post-translational modifications than the other two systems.
They also have the best machinery for the folding of mammalian proteins and, therefore, give you the best chance of obtaining soluble protein when you want to express a protein of mammalian origin.
The disadvantages of insect cells are the higher costs and the longer duration before you get protein (usually 2 weeks).