Billierosie and Neve Black's places, lol). But it trips my switches for both "woah - hot" and "aaargh - completely freaky". I found it via Danielle de Santiago's blog but it originates in a French AIDS safety campaign. And there's a version with a woman and a giant spider too...
I've never written man/scorpion sex. But I did write some scorpion-man sex in my novella The House of Dust:
Then I see them, because when they move they generate a flickering light like the dance of distant lightning. There are four of them, scorpion-men, bigger than oxen. Their rear parts are the bodies of scorpions and from the front grow the bodies of men. All parts are covered in black chitinous plates, and when those plates rub together the light flickers into being, illuminating their staring faces. Venom-laden tails arc high over my head. There are no words spoken here. They take me from him and rip from me my torn and filthy dress.
(The House of Dust can be found in Magic and Desire.)