NES/Famicom Emulator fwNES 0.302b: This is  based On CYS's hacking. Full emulation of NES/Famicom hardware, memory mappers, and sound channels, and all device that NES/Famicom used. Click here to download

ZSNES version 1.17b: ^*Recommended ZSNES is a Super Nintendo Entertainment System emulator written mostly in assembler. http://www.zsnes.com   

click here to download

Hello Game boy: ^*Recommended This Emulator has a lot of feature, you can save stat and load stat that is recommended in some save game editors. Click here to download

NO$GMB nocash gameboy emulator:  It has a hex to cheat the rom. This is recommended when playing Pokémon crystal. And in using Pokémon Crystal Save Game Editor.  Click here to download

http://www.work.de/nocash  

Genecyst Version x.xx (xx/xx/9x): Genecyst is a DOS based emulator for the Sega Genesis. The 68K, Z80, DAC, digital FM emulation and graphics rendering were written from *scratch* in assembly. The rest is in C++.
It is freeware and it is not to be distributed with game
ROMs and it is not to be modified or sold. Loads roms in the BIN, SMD or split (*.1) file formats.    Click here to download