Toribash
Vox had a WIP script that sorta did it years ago (it controlled both toris), but it took days of leaving the game running before it would figure out staying upright let alone managing to fight properly.

Either way it was interesting to watch them slowly improve. The file it created did get horrifically big though since it stored everything that happened through thousands of matches.

No idea if anyone still has a copy of it handy though, it's from 2011/12 and was only passed around the staff on IRC.

<Erf> SkulFuk: gf just made a toilet sniffing joke at me
<Erf> i think
<Erf> i think i hate you