Oh god, I have read so many bad doujinshi. I'll put this under a cut to help spare anyone who doesn't want their eyes to bleed or puke:
Summary
There was one where during insertion there was some blood (yes, yaoi sex). The seme character rubs some of the blood on his fingers.......... AND THEN LICKS IT.
There was another one I read. I'll just say it was an m-preg. A very, VERY detailed m-preg. I've seen some pretty crazy doujinshi, but I think that one still has the reward for most f'd up.