There are plenty of cool iPhone 6 cases around. This DeLorean Time Machine case would make a nice gift for the geek in your life though. It features blue LED lights that illuminate when you get a call. There are also movable parts like fold-up wheels. The parts move, allowing you to use the camera or other smartphone features without having to take your phone out of the case.
Crazy Case DeLorean Time Machine needs 3 x LR44 batteries to work. It is currently available for the iPhone 6. You can find out more information about it here.