Ugh, coming up with something "cool" under time constraints, while someone is sitting there and watching my every move, is not exactly a realistic gauge of anything. One of the reasons the hiring process is so broken for so many is that they fail to take in to account the nervousness and pressure the candidate will invariably be feeling. Speaking as someone who has done many interviews, questions like this always make me cringe. Sitting there in a suit, sweating and angling for a job, isn't really the best time for me to come up with something "cool."