What optional rules do you guys play with? Which ones do you hate?
And on a highly personal note, do you allow for saves vs. death by massive damage?
(
Comic related.)
Here's my System Shock rules, which is closest to your personal question...
System Shock represents the body being pushed beyond its limits, and may be called for when:
• Creature fails its saving throw against a rogue’s Sapping Attack (see my
Class Document).
• GM might allow a Called Shot (BETTER INSPIRATION) to trigger a system shock roll.
• A resurrected creature’s roll on the DANGEROUS RESURRECTION table indicates system shock.
• Creature is pushed past its maximum exhaustion (EXHAUSTION REVISED).
• Creature recovers from a debilitating magical condition like petrification or being permanently polymorphed, and fails a DC 15 Constitution save.
• Certain weird magic, magic items, traps, or planar effects might require a DC 15 Constitution save against system shock.
d10 Effect
1 Target drops to 0 hit points and begins making death saving throws.
2 Target drops to 0 hit points, but is stable. It regains consciousness (1 hp) in 1d4 hours.
3 Target falls unconscious for 1d10 minutes.
4 Target falls unconscious for 1 minute, but may be revived by another creature taking an action.
5 Target falls unconscious until the end of their next turn.
6 Target is stunned and cannot speak until the end of their next turn.
7 Target is incapacitated and cannot speak until the end of their next turn.
8 Target can’t take reactions or attack and has disadvantage on ability checks until the end of their next turn.
9 Target can't take reactions and has disadvantage on attacks and ability checks until the end of their next turn.
10 Target can't take reactions until the end of their next turn.