Wall of pain
Wall of pain (abbreviated "WoP") is a Jigglypuff technique of barraging the opponent with fast aerial attacks, exploiting Jigglypuff's horizontal air speed to weave back and forth. It can be used to juggle enemies offstage.
Smashers Tetsuya and AOB were the earliest prominent users of the technique, and they are largely responsible for its widespread use (see PuffStuff). The term "wall of pain" was coined by Smash World Forums administrator and retired smasher Amorasaki, a longtime friend of AOB. One of the most famous examples, commonly demonstrated by pro smasher King, is the use of Jigglypuff's multiple back aerials to juggle an opponent off the stage horizontally.
 See also
Other characters with the ability to jump multiple times in mid-air, such as King Dedede, Pit, Meta Knight, and Kirby, can attempt similar techniques as Jigglypuff's Wall of Pain. However, with slower air speeds, faster falling rates, and moves with varying directions and knockback, these attempts are less effective than Jigglypuff's original WoP. Charizard, Snake, and R.O.B. with Robo Burner are not listed, as they only have two midair jumps or an up special as their multiple jumps. They can in no way reflect a truly effective wall of pain.
Those characters with a somewhat established "WoP" are as follows:
 Fence of pain
The fence of pain (abbreviated "FoP") is a term refering to using Kirby's back aerial consecutively in a single jump, as both a defensive and offensive maneuver. The term is based on Jigglypuff's "wall of pain", due to direct similarities between the two tactics, yet it's called the "Fence" of Pain, because "it has many more holes than the Wall". Due to Kirby's increased midair movement in Brawl, this technique is much more effective, arguably enough to be called a type of WoP.