I would suggest you to do a project related to the field in which you wish to specialise later.
For example you can do core hardware projects using basic electronics components, with minimum ICs if you wish to master in hardware. You better do some microcontroller based project if you wish to concentrate on embedded system field. You can also do Matlab projects, if you wish to concentrate on DSP field. If you aim at VHDL field as your career, you can do some FPGA related project.
After your course completion, what make you different from others is your experience in the mini and main projects you’ve done.
Lot of topics are available in the net. Choose brilliantly!