Penguin Mario

Penguin Mario is a power-up that first appeared in New Super Mario Bros. Wii. He becomes the Penguin Mario after gathering a Penguin Suit. After Mario has become this form, he can throw ice balls at enemies and freeze them. Mario can then use the frozen enemies as platforms or pick them up and throw them against the wall or other enemies. He also gains a good traction on ice, stopping him from slipping, like normal Mario. While in this form, Mario can slide on ice with great speed, defeating some enemies and destroying Brick Blocks, allowing him to find secret areas. If he gets a running start, Mario can also slide a considerable distance on the surface of water, and can jump up from the water to maybe get a Star Coin or block. Also, Mario can swim a lot better in this form, with much more accuaracy and precision, like Frog Mario did in Super Mario Bros. 3.

Mario & Sonic at the London 2012 Olympic Games
Although Penguin Mario himself doesn't appear in the game, there is a suit based on him that the player can unlock for their Mii to wear. It is one of the suits unlocked after paying 10 blank cards.

Trivia

 * Penguin Mario's special abilities are very reminiscent of the abilities of Shell Mario from New Super Mario Bros., which include better and faster movement underwater and sliding into enemies to defeat them. Penguin Mario, however, requires ice beneath him to properly slide and seems to be slightly weaker than Shell Mario, since sliding into Dry Bones won't defeat them.