A lazer (a type of laser fired by Shoop da Whoop and similar) is a common, very overused element in YouTube poops.
Lazers are pulsating beams of blue light that usually come from a person's mouth. Anyone standing in the way of a laser would be injured or killed.
The lazer first appeared as scene of Dragon Ball Z (Episode 157) where you see Cell's expression on 1:28. Later people officially made the first Shoop da Whoop video called "The Lazer Collection", a three part reel that featured these beams being used to kill people.