
Avoron |
Strength, Wisdom, or Charisma damage or drain will knock a creature unconscious once their ability score falls below 1. So any method of distributing those can make a creature fall unconscious.
In addition to drow poison, several other poisons can cause unconsciousness without needing to reduce an ability score to zero: blue whinnis, maiden lily attar, oil of taggit, and purple pesh.

Sergeek The Mad |

what do you need it for?
To make someone unconscious :^)
Just wanted to know if it is still possible to get this condition if you are immune to nonlethal and have ferocity.Thanks for replies! It seems that dedicated poisoner can do it, but maybe there are other option? I know some illusion color based spells to knock you out, but only if your HD are scarce.

Avoron |
Here you go:
Color Spray spell
Disabling Palm monk of the mantis ability
Fleshnet Cannon
Icy Tomb major hex
Incapacitate bounty hunter slayer ability
Knock-Out Blow rogue talent
Knockout brawler ability
Knockout wildcat monk ability
Mass Suffocation spell
Master Slayer slayer ability
Quivering Palm Versatility feat
Rebuke Technology spell
Scintillating Pattern spell
Skullcrusher Gauntlets
Sleep Venom feat
Sleeper Hold feat
Sleeper Hold strangler brawler ability
Suffocate kineticist wild talent
Suffocating Strangulation feat
Suffocation spell
Zortaphen

Doki-Chan |

Diseases ; the new tracks (as long as they keep failing the Fort save, though that's not very likely...)
Also environmental effects such as:
- Suffocation (although in your case not Slow Suffocation)
A character who has no air to breathe can hold her breath for 2 rounds per point of Constitution. If a character takes a standard or full-round action, the remaining duration that the character can hold her breath is reduced by 1 round. After this period of time, the character must make a DC 10 Constitution check in order to continue holding her breath. The check must be repeated each round, with the DC increasing by +1 for each previous success.
When the character fails one of these Constitution checks, she begins to suffocate. In the first round, she falls unconscious (0 hit points). In the following round, she drops to –1 hit points and is dying. In the third round, she suffocates.
- and Drowning
Any character can hold her breath for a number of rounds equal to twice her Constitution score. If a character takes a standard or full-round action, the remaining duration that the character can hold her breath is reduced by 1 round. After this period of time, the character must make a DC 10 Constitution check every round in order to continue holding her breath. Each round, the DC increases by 1.
When the character finally fails her Constitution check, she begins to drown. In the first round, she falls unconscious (0 hp). In the following round, she drops to –1 hit points and is dying. In the third round, she drowns....../.....
It is possible to drown in substances other than water, such as sand, quicksand, fine dust, and silos full of grain.
So, you may be able to drown or suffocate the character in a controlled fashion if you have enough planning? Maybe a spell or bestiary monster with an ability?