(0001) GaN single crystals having a thickness of 3.4 mm and a density of in-grown dislocations of 3.5 x 106 cm-2 have been deformed at room temperature using a cube corner, a Berkovich and a Vickers indenter, respectively. Cube corner indentations were performed in a scanning electron microscope in order to observe the deformation in situ. Subsequently, cracks and dislocations at the indentations were investigated by means of optical microscopy, scanning electron microscopy in secondary electron contrast and cathodoluminescence imaging. The arrangement of dislocations is determined by the symmetry of the indented surface. In contrast, the formation of cracks depends on both the shape and the orientation of the indenter.