A gimp kill is a very low-percent KO that can put a really large swing on the outcome of a match. Fox's Shine spike, Marth's d-tilt and spike, Link's Spin Attack, and Fox and Falco's Down Throw are very effective for gimp KOs, and Marth's game in particular became very conducive to a variety of gimp kills with the generation of pros such as Mew2King and KoreanDJ. Gimp KOs range from large knockback moves, spikes, edge-guarding, as well as various other techniques. They are most effective on characters with low vertical and/or slow recoveries, like Link and Donkey Kong.
Fox & Falco
Fox and Falco's Down Throw are an effective gimp KO only if they grab their opponent while they stand on the edge of the stage. Fox's gimp KO works on all characters, including heavy characters, such as Bowser, but unfortunately Falco's only works on those lighter than him or equal to his weight and those with a fast Falling speed, such as Kirby. If Falco uses this on someone heavier and or with a slower falling speed than him, they will only fall halfway and they will need an extremely high amount of skill to be perfectly executed. If done correctly, Fox or Falco will do a very powerful Judo Slam and quickly shoot their opponent down so far that they won't be able to recover no matter how effective their Recovery is. This is either a sweetspot or a glitch of Fox and Falco's Down Throw and will be considered a Meteor Smash. This method does not work on stages such as Onett, Mute City, or Flat Zone 2, where there is no edge that, if the opponent is meteor smashed from, will fall. Although most gimp KOs are harder to master, doing a gimp KO using Fox or Falco's Down Throw is one of the quickest, strongest, and easiest gimp KOs of all. It can kill anybody at a damage percentage as low as 4 to 5% and may sometimes be a OHKO if you're lucky. A simple way to do this is to Camp, throw your opponent off the stage, and Grab your opponent when you have the chance to stand on the edge of the stage. Roll Dancing will come in handy. Try practicing this on a flat stage such as Pokemon Stadium or Final Destination. To stand on the very edge of the stage, you must hold the Control Stick Up at an angle while walking toward that edge's direction.
Link's Spin Attack focuses a high amount of knockback at its edge. Link can throw off his opponent and use Spin Attack to send his opponents far and edge-hog for an effective gimp KO.