Big Thwomp

Super Thwomps are a sub-species of giant Thwomp that have made semi-recurring appearances throughout the Mario series. Although their size varies between games, it is always shown that they are larger than the other Thwomps seen alongside them in the games. They also have the ability to smash through certain types of Brick Blocks and tiles, something that their smaller counterparts are usually incapable of doing.

New Super Mario Bros.
In New Super Mario Bros., they act just like Thwomps as they will come down from the ceiling in an attempt to squish Mario; the only differences are that these enemies have the ability to smash through Brick Blocks and are larger in size. They also have the same weaknesses as their smaller counterparts, being able to be defeated by either a Starman, as Shell Mario, or as Mega Mario.

New Super Mario Bros. Wii
Super Thwomps reappear in New Super Mario Bros. Wii as well. However, they only appeared in the World 1 Castle. They are not seen smashing through Brick Blocks; instead they are seen smashing through white tiles on the floor of the castle.

Super Mario Galaxy 2
Two Super Thwomps appear in Super Mario Galaxy 2 in the Supermassive Galaxy. They are much larger and wider than normal Thwomps, and Mario can still wall jump up them just like the normal ones. There are 2 1-Up Mushrooms on top of them.

Trivia

 * Super Thwomps may have made their first appearance in Super Mario RPG: Legend of the Seven Stars, because in Bowser's Castle, the last Thwomp is much bigger than the other Thwomps.