Things like milkers, auto dildos, electro stimulation, portals, tickle machines? Milkers could be used to give pleasure to the subject or your character. Auto dildos for fucking. Etc.

i want a way to control the oxygen intake of a subject. I want a way to use a mask or a gag-type thing that lowers the subject's oxygen intake limiting them to only breathing a little bit or not at all. This could be a way to punish the subject when they disobey or something if you want to make them submissive

The detachment of appendages, which can range from the the small (hand, genitals, etc.) to the big (entire lower body, head, etc.), without, and I repeat, without killing or harming the subject or yourself. No blood, no gore, the goal of this is not harm. 

I have absolutely zero idea if this is even possible in the programming of the game, but if it is, I would imagine an item like a 'detachment band' being used to wrap around certain parts of the subject's body, or your body, to detach them.

Basically a little (insect to small rodent -actual sized) creature, as a tool. Various method/styles depending on body parts/size challenge.

i feel like stuffing and water/air inflation would fit right into a game about furry science