
UnArcaneElection |

Martials don't need a sea anchor around their neck, so no fumbles, auto miss is enough.
Edit: As an example, I've done knife work in kitchens for over 15 years now and cut myself once. A 1 in 20 chance for a f+*~up is too damn high for people who know what they're about.
This reminds me: Back around 1980, when I was playing 1st Edition AD&D with my friends, one of them was DM in a session in which I was the only player (the DM's brother was not there at the time), and brought in some Fumble rules (I forgot where these were sourced from), and in the course of hacking away Shriekers (which either never managed to attract wandering monsters or only attracted some fairly insignificant threat, my Paladin went from having 2 picked up allies to being solo.
Not sure if such things existed in Metamorphosis Alpha or Gammaworld (TSR's closest equivalents to Starfinder at the time, to which I had no exposure) or Alternity (TSR's closest equivalent to Starfinder in the later part of 2nd Edition DUD time, to which I had no direct exposure but did follow a PbEM) had similar critical fumble tables floating around for them, or for that matter if original Traveller (available in 1st Edition AD&D time, but which I had only very limited contact with).

Eletj |
In a game with fumbles and hit locations, a barbarian did the following:
1. Charge.
2. Critical Fail, roll on crit fail chart -> hit self.
3. Roll to hit self. Critical hit. Head severed.
So what you see is a barbarian charge at someone then swing his axe at full strength and cleave his own head off.