A list of Emulators usable right within your browser.
EmulatorJS: https://github.com/EmulatorJS/EmulatorJS Scroll Down to "Demo" and click on it. You should now be taken to a prompt to insert a rom. Check the github page for supported systems. Has Cheats support.
Retroarch: https://retroarch.nenge.net/ A reliable fast port of Retroarch. Currently only supports Nintendo and Sega consoles, though it appears you can add more cores to it.
N64Wasm: https://www.neilb.net/n64wasm/ (NOT RECOMMENDED ON SLOW COMPUTERS)
GBA: https://web.skyemu.app/ supposebly the "Most Accurate GBA Emulator" for your browser.
Nintendo DS: