A NES emulator I wrote for my own enjoyment. Supports NTSC mappers 0-4 (about 80% of the North American library).
Below are instructions I wrote in case I forget how to compile on Windows.
Theoretically works on other OS since all of the libraries are cross-platform.

1. Install Visual Studio Community (C++ environment)
2. Clone repo
3. Install and setup wxWidgets 3.X
   3.1. Download zip containing source code from wxWidgets website
   3.2. Extract source code to its own folder
   3.3. Open VS project in <extracted_folder>/build/msw/wx_vc17.sln
   3.4. Build wxWidgets by going into build->batch_build..., Press Select All and then Build.
   3.5. Once build finishes, add the system environment variable WXWIN with the value <extracted_folder>
   3.6. Restart visual studio and open LilyNES solution (important: don't open the folder, open the solution).
   3.7. Right click the solution in solution explorer->Properties
   3.8. Change configuration to All Configurations
   3.9. Under C/C++->General->Additional Include Directories add "$(WXWIN)\include", "$(WXWIN)\include\msvc"
   3.10. Under Linker->General->Additional Library Directories add "$(WXWIN)\lib\vc_x64_lib"
4. Install and setup SDL2:
   4.1. Download SDL2-devel-2.X-VC.zip from: https://github.com/libsdl-org/SDL/releases
   4.2. Extract zip content to its own folder
   4.3. Download SDL2-ttf-devel-2.X-VC.zip from: https://github.com/libsdl-org/SDL_ttf/releases.
   4.4. Extract the SDL_ttf.h and place it in <sdl_extracted_folder>\include
   4.5. Extract the SDL2_ttf.lib and SDL2_ttf.dll files and place them in <sdl_extracted_folder>\lib\x64
   4.6. Add environment variable "SDLDir" with the value being <sdl_extracted_folder>
   4.7. To the system PATH environment variable, add <stdl_extracted_folder>\lib\x64
   4.8. Restart visual studio and open LilyNES solution
   4.9. Right click the solution in solution explorer->Properties
   4.10. Change configuration to All Configurations
   4.11. Under VC++ Directories->Include Directories add "$(SDLDir)\include"
   4.12. Under VC++ Directories->Library Directories add "$(SDLDir)\lib\x64"
   4.13. Under Linker->Input->Additional Dependencies add "SDL2.lib", "SDL2main.lib", "SDL2_ttf.lib"
5. Install and setup Boost:
   5.1. Download zip from Boost website
   5.2. Extract zip content to its own folder
   5.3. Add environment variable "BoostDir" with the value being <boost_extracted_folder>
   5.4. Run bootstrap.bat in <boost_extracted_folder>, and then run b2
   5.5. Restart visual studio and open LilyNES solution
   5.6. Right click the solution in solution explorer->Properties
   5.7. Change configuration to All Configurations
   5.8. Under VC++ Directories->Include Directories add "$(BoostDir)"
   5.9. Under VC++ Directories->Library Directories add "$(BoostDir)/stage/lib"
6. Build LilyNES in release mode

Features include save states (8 slots) and rewind.
A feature I never implemented because I couldn't be bothered: changing key binding.
So you're stuck to the default: A=X, B=Z, START=S, SELECT=A, D-PAD=directional keys.
Save state: CTRL+#slot number (CTRL+1, CTRL+2, etc...)
Load state: #slot number (1, 2, ...)
Rewind keys:
R = Start rewind/cancel rewind, W = Previous state, E = Next state, Q = Continue from current state