Just based on timing, these were "lucky" punches...

JC Chavez-Meldrick Taylor

Acelino Freitas-Jorge Barrios

Both JC and Freitas were behind on points and in both fights time was slipping away.

I guess you could add Marciano-Walcott in there but he set that punch up and timed it perfectly so I don't think its "lucky" that it landed or that it kept Walcott down.