Interesting. From this thread, we've learned that the following characters are Falco's counter:
G&W
ROB
Metaknight
Lucario
Zelda
Wario
Pit
DDD
Kirby
Mario
Olimar
Pikachu
Jigglypuff
Marth
Lmao...
G&W: I don't think anyone is going to question this one. The DThrow to DSmash is guaranteed if I recall, the Lasers can be caught via Bucket and used against you, he's hard to CG, hard to spike due to his good recovery, and his Melee out prioritizes Falco by far.
Meta Knight: I would have to say Meta Knight has a slight advantage here. Meta Knight is able to gimp Falco pretty badly if he brings him off the stage, which with a few throws and his amazing dash grab, wouldn't be too difficult to do. Meta Knight is faster, and his Melee is superior. He also can't be spiked easily save for CG to Dair, due to his awesome recovery. It isn't a major advantage since those Lasers and CG are a problem, but this one goes to Meta Knight.
Jigglypuff: I've already defended this point.
Kirby: Due to subtle similarities Kirby shares with Jiggs (multiple floats, ducking under lasers, good edge guard), I'm going to go on a limb and say Kirby has the advantage. But don't quote me on this, as it may be a farfetched assumption, and Kirby does not have the mobility Jiggs does. Kirby also has his Psuedo CG with the FThrow to UTilt.
Pikachu: Pikachu is faster than Falco, both in the air and on the ground. Even though Falco can CG Pikachu, Pikachu will CG you back, and to a higher percent. Pikachu also has two he can use against you, and one brings you to the edge of the stage for a gimp. These are statistics I can go by, but in terms of experiencing this match up, I can't really say much. I think Pikachu has the definite advantage in this one.
The rest of those characters, save for maybe Wario (which I don't feel I can really make the call in), are either even with Falco or are at a disadvantage. Just my opinion.