Stop Watch

Pull up four large vegetables in Super Mario Bros. 2 and the 5th plant will be a Stop Watch. It will appear for a second and then freeze everything and everyone temporarily. If Mario needs any Small Hearts, this is a good chance to kill some enemies so they can appear.

The Stop Watch is later seen in the Paper Mario series. When Mario uses this item, if it works it will immobilize enemies for a few turns. It can be bought at most stores and is a fairly common item.