Nin is an advanced Nintendo Entertainement System and Famicom emulator that is actively being developped.
Right now, the emulator is not very polished on the UX side, but can run many games without issues. A gamepad is supported. The exact mapping will depend on the vendor's layout. On a keyboard, the arrows are mapped to the NES D-Pad, Space is Select, Enter is Start, Z is A and X is B. Multiple controllers or other kinds of controller are not currently supported.