Post apps you think noone else knows about or obscure apps that blow your mind. Then we make a list.
Vice
VICE is a program that runs on a Unix, MS-DOS, Win32, OS/2, BeOS, QNX 4.x, QNX 6.x, Amiga, Syllable or Mac OS X machine and executes programs intended for the old 8-bit computers. The current version emulates the C64, the C64DTV, the C128, the VIC20, practically all PET models, the PLUS4 and the CBM-II (aka C610/C510). An extra emulator is provided for C64 expanded with the CMD SuperCPU.
https://vice-emu.sourceforge.io/
Cool Retro Term
cool-retro-term is a terminal emulator which mimics the look and feel of the old cathode tube screens. It has been designed to be eye-candy, customizable, and reasonably lightweight.