Save converters can change a save from one format to another. Emulators can sometimes use a different file format.
PS1
MemCard Rex
http://www.emucr.com/2013/06/memcardrex-v17.html
PS2
mymc
http://www.csclub.uwaterloo.ca:11068/mymc/
Game Boy Advance
gbaconv
Converts GBA battery saves between VBA-M and the VBA-Next core of RetroArch. Note that most games will work without conversion, but some may break entirely without converting (e.g. Ninja Five-O).
https://github.com/libretro/vba-next/tree/master/libretro/gbaconv