FCE Ultra is an NTSC and PAL Famicom/NES emulator for various 
platforms. It is based upon Bero's original FCE source code.  Current
features include good PPU, CPU, pAPU, expansion chip, and joystick
emulation.  Also a feature unique to this emulator(at the current
time) is authentic Game Genie emulation.  Save states and snapshot
features also have been implemented.  The VS Unisystem is emulated
as well.  FCE Ultra supports iNES format ROM images, UNIF format ROM
images, headerless and FWNES style FDS disk images, and NSF files.

FCE Ultra currently supports the following iNES mappers(many partially):

WWW: http://fceultra.sourceforge.net/