WWF No Mercy

I think you run towards the ropes and press grapple just as you hit the ropes. Not all players can do it though. The lighter players will do lionsaults, the middleweights will spring off the ropes with a backward elbow, and heavyweights wont do anything. To check for sure, go to the options where you edit a players moves. There should be a section somewhere about moves as you run into the ropes. That will show you for sure what buttons you need to press and what move the wrestler will do.