PlayGuy is an emulator for the Game Boy Color that offers Full CPU core emulation. It offers a vast majority of the support for Game Boy carts. Full emulation of the audio among other features that have become standard for emulators such as filters. With the also added benefit of the real-time clock support.
The development of PlayGuy has sadly ceased despite making fairly good process, with the website now offline and no new versions been seen since 2007.