I was hooking up with a girl who told me she had dogs. First time I went to her house, they were 3 giant pits.
We went to the bedroom to get it in, and she told me she had trained them to attack if they heard her say, "ouch," which she said a LOT.
It was hand over the mouth, face in the pillow that whole session. I never went back, all subsequent meet-ups were at my crib.
Edit: I do have to say to their credit, they were very nice and playful, and they loved me, so I didn't have any issue with them, I just didn't want to take any chances