I vote... huh. Energy Tank for 100% recovery, Heart Container for full recovery, Maxim Tomato for 50% recovery (Kirby usually had six hits), get rid of food entirely, Skip Sandwich Deluxe for full health revocery and bunny hood effect (awesome idea thar, Chrono26). Actual Poison Mushrooms that do actual damage in large amounts (20%+), unlike the Poison Mushrooms that make you smaller.
Spider Ball lets you run on walls temporarily - use it to hide under the stage for a while, but if you stay too long, you get stuck. The Mirror Shield pickup temporarily deflects energy projectiles (I.E. Samus' Charge Beam, but not her missiles), Bomblings replace or are added without replacing bombombs, and have the ability to walk up walls (meaning no hiding behind low barriers bombombs can't cross), Kirby's Jet ability returns to augment jump power (but not speed), the "Sleepy" enemies from Kirby Superstar that, upon being touched, will make your character fall asleep temporarily, P-Wing lets you jump infinitely (again, temporary).
Please, someone continue.