Shiki no Uta.
Jigglypuff invalidates like half of Falco's entire moveset. The endlag of Up Smash gets punished, Side Smash is too slow even as a punish, Down Smash and Dtilt won't hit Jigglypuff unless it's on the ground for some reason, Fair becomes risky because its startup, Bair would be nice if Falco could catch up to Jigglypuff, Dair is a no-go unless you know exactly where Jigglypuff will be, Falco Phantasm isn't that useful since it's telegraphed ever so slightly, I don't have to explain why you wouldn't use Fire Bird do I, and Jab combo can be interrupted by Rest, Bair, and anything else in Jigglypuff's arsenal. Grabs aren't exactly easy when Jigglypuff has good mobility and Falco doesn't.
That leaves Nair, Uair, Ftilt, Utilt, Reflector, Dash Attack, and Blaster. Of thoe moves, only Uair and Utilt reliably kill while Nair can kill if all hits connect which they won't usually. Reflector still remains as a good spacing tool, Blaster can still be used for free damage, and Ftilt is the main way I get damage on Jigglypuff. Dash Attack is also decent for damage and getting Jigglypuff away.
The same goes for Rosalina since she can 0% death juggle him because Falco's air speed is horrible and fast-falling means it's much easier for Rosalina to keep juggling. Palutena can sort of do this, but I believe Palutena doesn't jump as high and falls faster than Rosalina making it a bit more manageable. Personally, I believe that Jigglypuff shuts Falco down while Rosalina comes close since to it, but I rarely fight her, so I can't say entirely. Still, I have never heard of a character in SSB4 being shut down that hard.
At least Little Mac is fast, so fighting Jigglypuff would be like trying to control Jigglypuff on the ground while Jigglypuff tries to control the air. Even Diddy Kong is manageable with Falco. Why? Because Falco hits as hard as Diddy. Watch Keitaro's Falco vs. Diddy and it seems like Diddy does have an advantage, but not a you can't do **** against this matchup. If anything, Falco might be one of Diddy's more even MUs - in terms of Super Diddy Bros. MUs, of course.
The other issue is For Glory. Do I need to say anything? Jigglypuffs will usually stay on one end of the stage or float about which is freaking annoying and the whole Final Destination policy makes it difficult since I bet with platforms, this MU would not be as ********* difficult.
Duck Hunt infuriates me because of all those projectiles which is Duck Hunt's game plan, so whatever.