Here's my take, look at what is the source/cause of the effect.
If a player was slipped...lets call it 'jamba juice'. It's not magical (like a potion), and it causes the same dice penalties and bonuses inebriation causes. You can't really justify it as anything else but poison or disease (maybe because it has bacteria in it) as the cause.
I'd rule that ...
If you allow DMG poisons, yes, it may be a problem
The reason, e.g., Purple Worm poison is not broken is that it can only be applied once per dose, which is quite expensive (2000 gp), and applying it takes an action, so it is essentially a "first hit burst" type of damage. Using your dagger, it is now essentially a 1 hour buff, so the adventurers ...
RAW questionable, but probably not
Note that there’s nothing that inherently stop this from working initially – a familiar can perform actions, and applying poison to a weapon is certainly an action.
However you put it though, an Action needs to be something that the creature taking that action is physically capable of doing. There are of course no explicit ...
RAW, this works.
Find familiar states:
A familiar can't attack, but it can take other actions as normal.
One of the actions listed as an example for "the sorts of thing you can do in tandem with your movement and action" is:
withdraw a potion from your backpack.
Since a familiar may "take other actions as normal", I would rule that a ...
This simply isn’t defined anywhere in the rules. There is no technical definition of “immunity,” and it is very likely that the original authors never even considered the question, since in Core, it would never make a difference. (And, truly, even outside Core, it is very, very rare for it to matter anyway.)
Trying to read between the lines in the rules for ...
Rules as written, this works. Whether or not this is intended is up to your GM.
From the SRD:
When a character takes damage from an attack with a poisoned weapon, touches an item smeared with contact poison, consumes poisoned food or drink, or is otherwise poisoned, he must make a Fortitude saving throw. If he fails, he takes the poison’s initial damage (...
No, they don't.
Saving Throws (PHB p.136):
Generally, when you are subject to an unusual or magical attack, you get a saving throw to avoid or reduce the effect.
If you're immune to poison, there's nothing for you to avoid or reduce against a poison effect, it does nothing to you.
Also, making a saving throw would imply throwing dice, which would ...