I watched a MSG match between Haku and Davey Boy Smith from October 1990. It might have been Davey Boy's first match back since leaving a few years before, and just after the bell rings Haku reaches over and they shake hands. It's not really noticed by Gorilla Monsoon and Alfred Hayes, but it certainly sticks out as being uncharacteristic during this time. I also heard about a match from around this time between Roddy Piper and Curt Hennig that was for a TV taping, where at the end Roddy stuck out his hand and they shook.
Are there any other times where this has happened?