I wasn't able to speak much last night. The Cape also appeared(though it's only for Super Baby Mario) in Yoshi's Island, so it's not just one game.
It's hard to say which is more iconic of an item, regardless. SMW being a very iconic game(more than Sunshine) doesn't correlate for an item, so I'll concede that point.
The other thing I wanted to note from recent posts is that many think Mario should use his hammer. "No one wants that" is not a good point to bring up. Just speak for yourself, really. I don't see bringing out weapons from thin air as some kind of odd thing. That's how a ton of games do it, especially fighting games. Projectiles in general are effectively the same point. Mr. Game & Watch has charm, sure, but Link's been doing it for ages too. Bow, Boomerang, Bomb(same with his two clones).
That doesn't mean adding a weapon makes a character flow well. I haven't played Byleth enough to judge. But Ganondorf feels fairly weird. The sword used is the same model from the tech demo where his own model was used. I remember reading they planned to use the sword, but I don't remotely remember the source. The sword's model is fully in the game, not just cinematic, so it actually is among the model pieces. Doesn't mean necessarily it would've been used outside of victory screens or taunts, though. But it was literally made for the specific model, so it arguably flows rather well due to that alone.