Ledgehopped double laser
The Ledgehop Double Laser or LHDL is a technique that can be performed with both Fox and Falco, though it is far more useful and common among Falco players due to the superiority of his laser.
The technique, popularized by Japanese Falco player Bombsoldier involves ledgehopping by releasing the edge and jumping immediately, firing off two lasers by tapping B twice, and landing on the stage. Though it sounds simple in theory, the real trick is having your lasers travel at the proper height that you want.
If you simply ledgehop as you normally would and tap B repeatedly, you will likely end up with two lasers that are extremely high and not at the same height. So the proper way to LHDL requires you to drop from the edge a small amount further than you normally would, and to start tapping B immediately after jumping, on the way up, so that you fire one laser as you pass the ledge going up, and the second as you fall back onto the stage, at the same height.
A variation on this, that doesn't involve ledgehopping at all, is to run off the stage, drop for a bit, and use your midair jump to reverse double laser back onto the stage.