I wasn't allowed a soldering iron as a kid, so I ended up just chopping and splicing a regular serial cable and turned it into a null modem, all so that I could play OMF2097 with my friends without having to share the same keyboard (we would always fight over right side, which defaulted to using the arrow keys for movement - and so the person who got the right side generally had the advantage, as back then arrow keys were the default movement keys, unlike these days where WASD is default.)

I wasn't allowed one either so I soldered with a screwdriver heated up on the gas stove when my parents weren't home...

Shared-keyboard OMF 2097 also had an overwhelming advantage for the first mover, since most keyboards had 2-3 key rollover--if you hit wd to jump forward, your opponent had to be fast to do anything before you hit your attack key.