Wikipedia
NESticle is an NES emulator for DOS, created by Sardu of Bloodlust Software. Released on April 3, 1997, the widely popular program originally ran under DOS and Windows 95. It was the first freeware NES emulator, and became commonly considered the NES emulator of choice for the 1990s. Initially offering few features and only supporting a handful of games, development proceeded rapidly and to expand usability such that NESticle is today credited with introducing the concept of recordable playthrough for emulation, as well as providing the capacity for users to create their own graphical hacks via an integrated graphics editor. In pioneering this heightened level of access for users, and providing the tools for fans to hack and remix familiar classics, NESticle has been credited by Spin as representing a milestone toward the development of video game music as a genre.
While the emulator is no longer updated and has become obsolete as other emulation projects have developed and improved, NESticle remains frequently listed among prominent top tier emulators and it is still regarded as a good choice for emulation on older ( 486 and earlier) computers.