In Course 1, climb the mountain and find the Bob-omb that is manning the water cannon (he is walking in place). Pick him up, jump, then press Z to drop him. He'll be suspended in mid-air!

There is an interesting side-effect to this glitch: When the Bob-omb explodes, get the Coin that appears, then leave the area. When you come back, the Bob-omb will be back, except he will never attack Mario! If you didn't get his Coin, he will attack.