All moves that are intentionally meant to break shields not counting the bowser bomb, Ryu's f-tilt, and yoshi bomb. Give them shield pushback and only that. The moves themselves aren't necessarily bad, except for jigglypuff's pound, because even hitting a shield with it perfectly spaced means you get grabbed, which is stupid considering shielding pretty much beats jigglypuff consistently. It is only fair that even if I don't break your shield, I should still not be punished, but believe it or not, it happens sometimes for not spacing it too well, despite having clearly punished the player. Why Ryu's f-tilt? I believe it multi-hits. Why both bowser bomb and yoshi bomb? Because if you happen to use it as a OoS option or against a shielding player right next to them, if they don't react quick enough it is a free shield break, and both of those character already kill pretty easily so just making those moves even safer for them to use and removing your want of using a shield against them would be bad. Considering yoshi has some projectiles that come out of his down b which is annoying enough already making it harder to punish than bowser's that would be too good for him. Also both of those moves have a sliding tech so another reason not to give them more.
Even if you don't do it for the whole cast, please just do it for jigglypuff, all she really needs for a buff is a kill throw, a combo throw that can lead into a rest, a throw that is good for pushing the player away at an awkward angle for a free jab reset preferably back throw since forward throw would be the kill throw and up-throw the combo throw. Anything that just makes it scary for the opponent to shield against jiggs.