Have a few to add.
Couple Corruption:
Maybe a straight-laced married couple, or an innocent pair of high school sweethearts dragged or seduced into something far less vanilla.
Rape by Proxy:
It can go with the above, but a pair or more of unwilling participants forced to have sex with each other, with little or no direct involvement by the coercing party.
Micro Gang Bang:
Back to the faeries, but this time many of them. Imagine a swarm of faeries licking and groping you all over.
Or maybe a splitting potion that lets someone multiply themselves with a "conservation of mass" limitation. (For example you can have a dozen of yourself, but each one is 1/12 your normal size)
You know, just a lot of tiny partners at once.