Like its predecessor, Mario Strikers Charged is probably one of the most chaotic games I have ever played. I've often described it to people as, "Super Smash Brothers meets Soccer."
Officially the second game released by Nintendo to make use of the Wii Connect24 functionality, Strikers allows you to take on opponents outside of your living room. You can take on friends by sharing your 'friend code', or you can take on random people in a best of 3 match. You can also play an online series "with a guest," allowing two people to don their wiimotes and nunchucks as a team.
The game is centered around soccer, but maintains that marioesque game by adding a number of in-game powerups - from shells to bob-ombs to stars. Instead of having penalties, your opponent is given a powerup when you hit them illegally. Needless to say, a hard-hitting match can often result in a large number of items filling the screen. Not to mention "natural" hazards on the number of different fields, and the game becomes absolutely chaotic.
Single player, in-home multiplayer, and WiiConnect multiplayer all provide hours of endless entertainment. Very kid-friendly (and still a lot of fun to those of us who grew up with the Nintendo franchise).