Here is a cool gift idea for retro handheld gaming devices. The GameSir Pocket Taco turns your smartphone into a retro handheld with a D-pad and ABXY buttons. It has Bluetooth connectivity and works with iOS and Android devices. It is compact enough to fit in your pocket. The Pocket Taco is smart enough to turn on when you unfold it and shut down when you close it to preserve battery life (600mAh).
This controller also has a keyboard mode, in which you can remap its keys to your favorite layout. It is designed with soft silicone pads not to scratch or damage your phone. Pocket Taco supports passthrough charging. The GameSir app lets you customize the controller and button mapping. This controller weighs only 2.19oz. You can find this project on Kickstarter.
