What's your favorite power-up


love this design
My favorite is the Penguin Suit. It looks so cute and is very useful!
Red star, the most underused powerup in the Mario series. Nintendo probably recalled all of them but 2 because they realized communism isn't good or something. Also double cherries are fun. Also SM64 caps. Also hammer suits.
I've always tried to run away from the one up mushrooms that follow you around in Super Mario 64. But yeah, the Penguin suit, Propeller suit, Mario/Luigi/Wario caps, Hammer suit, and the Fire Flowers are great.
The Cape Feather, and I hate that it's only been used in Super Mario World and Super Mario Maker (2) levels using the World theme. It's really powerful, the yellow Cape Mario (and Luigi) gets from it compliments the colors of his usual fit very well, and arguably has the best flight capabilities of all the power-ups that allow Mario to fly!

(I'm not counting it's use in Super Mario Kart and Mario Kart 8 Deluxe; it's powers are extremely watered down when used on vehicles it seems)
The feather is a pretty terrible item in Mario Kart 8 Deluxe and it's exclusive to battle mode. It doesn't actually grant you any invincibility frames; multiple times in battle mode I've used it only to immediately get hit by someone's item, thus wasting the feather. The only good thing it has is that you can run into people with triple shells and steal a balloon from them (stealing a balloon is a great thing because you get severely punished if you lose them all) but the range is extremely small and the aforementioned lack of invincibility frames. It's outclassed by the Mushroom.