Jnes
Jnes is a NES emulator designed and programmed by Jabo (More known for his work on Project64 and his audio and video plugins for it).
Jnes boasts a high compatibility, managing to successfully emulate the graphics, sound, controllers, zapper and many memory mapping boards that are found in most USA games and even going as far as to offer support for memory mapping boards in some popular Japanese boards.
Alongside this it also features Kaillera for online gaming alongside other features such as instant saves and cheats. Jnes offer support for both the Microsoft Windows operating system and Android