The shine spike is one of Fox's edgeguarding techniques. It consists of using Fox's down special, Reflector (also known as shine, hence the technique's name), to semi-spike an offstage opponent in order to gimp them, preventing them from being able to recover. In Super Smash Bros. and Super Smash Bros. Melee, the shine spike is very effective, because of its instantaneous startup, trajectory of zero degrees (0°), and moderate knockback, allowing it to work even at 0%. Additionally, since the move slows Fox's vertical movement, it allows him to easily recover after a shine spike, especially in Melee where the shine can be jump canceled.
In Super Smash Bros. Brawl, the technique has lost some of its effectiveness. The shine now launches at a slightly higher trajectory of ten degrees (10°), which coupled with the generally slower falling speeds and better recoveries of the cast, allows it to be survived more easily. In particular, floaty characters, as well as those with either several recovery techniques (such as Wario) or a tether recovery, are usually able to survive it at low damage percentages. The shine's hitbox is also no longer instantaneous, hitting on frame 3 rather than frame 1, making it harder to intercept recoveries with it. However, the shine has gained low knockback scaling instead of having set knockback, increasing the shine spike's effectiveness at higher percentages, especially against characters who still have poor recoveries.
In Super Smash Bros. 4, Fox's shine has been further nerfed to the point of no longer allowing for true shine spikes. While keeping its 10° angle against grounded opponents, it now launches aerial opponents at a much higher 40° angle, no longer being a semi-spike. As a result, it has lost almost all of its utility as a tool for edgeguarding. Smash 4's changes to teching do provide a small boost to the shine's edgeguarding utility, however, as Fox can now pull off untechable stage spikes with his shine if the opponent recovers too close to the stage.
The Shine edgehog is a very useful technique for Fox offstage. It allows him to use his Reflector and grab the ledge after the move is done. First, the player must dash to the ledge. Before their momentum takes them off the edge of the stage, they must perform a Shine and quickly turn around in the air. (Note: This can be done without turning around, but turning around in the air gives more distance with the slide, plus Fox is then able to sweetspot the edge.) Doing it without turning around is practically useless, because it only goes so far, and players sweetspot the ledge before performing an unturned Shine.
This can be linked with a combo, like the waveshine. Characters with up special moves that meteor smash, including Ike and Kirby, can drag them down from the ledge, but if performed incorrectly, this tech allows a character to shine spike and edgehog.