I agree with Pure that you shoudl sty away from cars, spaceships, robots because they are done too much. But i think if you want to do one. MAke it spectacular. Do more than they expect and things they have never seen. Such as actually rigging the hole vehicule(doors, hood, trunk, even steering wheel). Have fully made dash and instuments and pedals, buttons, everything. Sometimes doing something thats been done a hundred times doesnt stand out. But if they start comparing if its a good car model by comparing it with yours you know youve done something right.