I think about this a lot when my mind wanders. Like obviously, the ones designed for survival are a given (ex: amputation, limb torture avoiding arteries, etc.)
But i think i could survive a wound fucking in the stomach as long as the intestines/organs aren't perforated and subsequent anti-biotics. Having watched a lot of surgery footage, often times surgeons hands are really rough with internal anatomy without negative effect. Maybe a bit more dicey if you use the intestine to wrap around a dick and stroke it off, since they might tear, but it's still pretty survivable.
I also think eye fucking, if not done too deep could easily survivable.
exsanguination that's calculated, with set up blood transfer for after could be done pretty easily. If done with SUPER precision, you could technically cut the trachea for a reverse blowjob while still allowing air to get through the bottom hole.