Re: Giant tentacled, furry bukkake in the ass.
My current big three, in order of favourite to least favourite:
Coolness:
Reptiles and metal creatures, living suits of armour. The more spikes, the more shiny, the more smooth, curvy, dangerous/evil-looking... the better.
Reversals:
Girl-on-tentacle, or play-as-the-tentacle. Futas. Sex when treated as combat, in which someone tries not to give in to their desires/orgasm, potentially because of some bad effect - Demon Girl for instance. Loli to a lesser extent, more so when the loli is experienced. Strangely, not yaoi.
Learning/Innocence & Corruption:
In which at least one of the parties is inexperienced/has no clue what sex is, or believes sex to be bad but is soon corrupted. Occasionally overlaps with the 'sex treated as combat' part. Loli are included inherently. Angles/Demons tend to feature significantly.
Potentially there are four, with the extra being weakness (largely a subset of fighting against pleasure, where the person gives in immediately).
I do not believe that it is possible to put this to a poll, due to the nearly unique nature of an individual's fetishes, and so have not voted. Still, a thread for listing fetishes is a good idea.