Mini Mushroom: You’re lighter, can jump higher, and can run on water. Can provide additional mobility.
Hammer Suit: You can throw hammers and kill even Boos and Thwomps with them. One of my favorite items in SMB3
Tanooki Suit: You get flight AND the ability to turn into a statue and hop on enemies you can’t safely jump on otherwise. Another favorite of mine in SMB3.