Turnip

Turnips are the first official vegetables that ever appear with their first appearance being in Yume Kojo: Doki Doki Panic. They are frequently found in Subcon, yet were originally found in the Real World.

Yume Kojo: Doki Doki Panic
Turnips only make an appearance in World 7-2 of Yume Kojo: Doki Doki Panic. They are produced from the Nightmare Machine, which the Arabian Family uses to throw vegetables at Wart's mouth to defeat him. The Turnips are the only effective items they could use as weapons against their foe to beat him. The bubbles Wart spits will fade way a Turnip if touched once.

Super Mario Bros. 2
Turnips make their first Mario game appearance in Super Mario Bros. 2. They now have a different version than that from Yume Kojo: Doki Doki Panic. This time, Turnips are planted in the ground everywhere in Subcon, especially in grassy regions of the world. Turnips can be picked up and thrown at enemies to kill them. The Nightmare Machine can also produce Turnips from it, and they can be used as weapons for Mario to injure Wart, like in Yume Kojo: Doki Doki Panic.

BS Super Mario USA
Turnips make an appearance in the direct sequel, BS Super Mario USA, and are used for the same purpose as in the earlier game. Sometimes, enemies can be turned into these vegetables by certain characters' spells.

Super Smash Bros. Brawl
For Princess Peach's down-special move, she pulls a turnip out of the ground and is able to throw it.