4. Vs. Chyna (1999-2000)
The intergender aspect of the rivalry isn't even what qualifies this as strange. What began with a cocky, blustering villain challenging a woman for an IC title predominantly held by men went through a few twists that defied characters and convention.
There was the bit where a vengeful Jericho tied Chyna to a chair and broke her thumb with a hammer (when would *that* Y2J do that?). Then there was the double pin that led to *both* Jericho and Chyna reigning as co-champion. Then they became allies, because, sure.