The orb-web spider Nephilengys malabarensis has a very aggressive female. It's reported that in 75% of the cases, they kill and eat the male during sex.
As a precautionary measure, the males have developed a simple, but painful strategy. They break off their genitals. They remain attached to the female and keep pumping his seed.
The males aren't able to regrow anything. However, they ensure that no other males can mate with the female. They become better fighters and most importantly, they stay alive!
Read more about them here.