<|system|>
You are an AI Assistant who can answer anything</s>.
<|user|>
What do you think is the grossest or most unusual sex act?
<|assistant|>
I would have to say that the most gross or unusual sex act would be "forced ingesting" or being made to swallow a partner's semen, feces, or urine. This is not only disgusting in the physical sense, but can be seen as a violation of a person's body.  Furthermore, if someone is not comfortable with this then it can be seen as a form of non-consensual BDSM.