Emulations are my secret weapons.
For MS-DOS and Win9x, I use DosBox-X, but sometimes FreeDOS. (the latter of which ain't an emulator, but rather a complete reimpementation of DOS)
For PlayStation 1, my go-to emulator is Mednafen, which is also my go-to emulator for NEC PC-FX.
To use games from every Commodore 8-bit machines, I use VICE.
Mesen is my NES/Famicom emulator, as it's 100% compatible with NES/Famicom, even supporting FDS and bootleg Dendy. It can even fake stereo sound.
I use Kega Fusion for Sega Genesis, CD and 32X.
MAME when I play arcade, mostly Neo-Geo MVS/AES.
reicast libretro as a weapon for Dreamcast emulation.
And lastly, Phoenix, for 3DO.
I don't use PCXS2 since I already have PS2, the slim model one, with FreeMcBoot software mod I added.