Stump

Stumps are objects found in Super Mario 64, Super Mario 64 DS, and Super Mario Galaxy. They can be Ground Pounded by any character, and may or may not result in something happening. They more resemble wooden pegs in Super Mario 64 and its remake, but are changed to look more like tree stumps starting in Super Mario Galaxy.

Super Mario 64 / Super Mario 64 DS
In Super Mario 64 and its remake, Stumps play a very minor role in the mission "Behind Chain Chomp's Gate" in Bob-omb Battlefield, where a Chain Chomp is tied to one. Ground Pounding on the Stump three times frees the Chain Chomp, who will in turn break the gate that was blocking a Power Star. Other Stumps are seen throughout Bob-omb Battlefield, but serve no real purpose. More Stumps are seen in the "huge" side of Tiny-Huge Island, but also serve no real purpose.

If Mario were to run around an un-ground-pounded stump five times in a row without interruption, five coins would fly out of them, but only once.

In these games, even if a stump is stomped all the way, the sound effect of pounding a stump will still play if Ground Pounded again.

Super Mario Sunshine
Although technically not stumps, nails behave near identically to stumps of Super Mario 64 in Super Mario Sunshine. They are found in various secret levels, such as Episode 3: The Hillside Cave Secret. Most give a Coin while some give a 1-Up Mushroom when fully ground-pounded into the ground. However, the player cannot run around an un-ground pounded nail to receive anything like in Super Mario 64.

Super Mario Galaxy
Larger Stumps reappear in Super Mario Galaxy in only the Gusty Garden Galaxy and the Gold Leaf Galaxy. When Ground Pounded, they turn red. They also now only need to be Ground Pounded once, as opposed to the three times from Super Mario 64 or Super Mario 64 DS. Ground Pounding on a Stump in Super Mario Galaxy may result in having two Goombas appear, two Flipbugs appear, many Star Bits appear, and very rarely, have a Life Mushroom or a Sling Star appear, or to get a giant Worm to move.

Super Mario Galaxy 2
Stumps reappear in Super Mario Galaxy 2 with the same design and function from Super Mario Galaxy. They still turn red when Ground Pounded. They only appear in the Puzzle Plank Galaxy, Cloudy Court Galaxy, and the Freezy Flake Galaxy.

Super Mario 3D Land
Stumps reappear in Super Mario 3D Land somewhat rarely, but with the same use as before. They leave only Coins. They do not turn red after being Ground Pounded anymore.

Yoshi series
In the Yoshi's Island series, similar objects called posts appear. Posts are obstacles in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, Yoshi's New Island, and Yoshi's Woolly World. They appear in many levels. They are wooden posts that come up from the ground, and Yoshi must Ground Pound them. In Yoshi's Island DS, Baby Donkey Kong can stomp them straight to the ground in one single ground pound. Coins and Red Coins can occasionally be found in these. They mostly block Yoshi's way and must be ground pounded. In Raphael The Raven's Castle, they are used to attack Raphael the Raven. Posts also appear in Yoshi's New Island and perform the same function. Ground Pound Rebound is one of a few levels to feature them.

Mario Party
In Mario Party, there is a minigame that has the player using ground pound on desired flat stumps and potentially spiky stumps. Ten coins are rewarded if the player ground pounds all five stumps.