This is what the game might be like IF it were made.
Items:
Red Shell/Green Shell (same functions as in Kart)
Bomb Omb (same as in Kart)
Banana Peel (again)
Mega/Mini Mushrooms (self explanatory)
Invinceability Star (again)
Screw Ball- Causes your character to roll into a "screw ball" shape dealing damage to any in his/her way and also going slightly faster.
Pitfall- Lays a trap that causes any foe who runs into it to fall into a hole.
Unira- Throws a Unira on the ground (basically does the same thing as in Brawl, except it can't be re-picked up and doesn't disarm itself until someone runs into it.)
Ray Gun- Your character picks up a ray gun (or their ride is armed with one). This ray gun has 5 shots. Each shot also causes a loss of 10% ride integrity.
Spicy Hot Curry- You are surrounded by fire, damaging any opposing rides near you.
Motion Sensor Bomb- Lay a trap. The next person (friend of foe) to run into this trap loses 50% ride integrity.
(Just a few item examples)
Smash Ball- Your character uses their Final Smash the next time B is pressed.
(Just a few examples)
Ike- Great Aeither, throws the sword way forward and quickly charges all the way to it. The sword causes a loss of 50% ride integrity to anyone hit.
Marth- Critical hit- Slashes forward, causing a 100% loss of ride integrity to any hit.
Roy (Yes he should be in this)- Flare Blade- Slashes forward (after 3 seconds) causing a massive explosion causing any hit to lose 100% ride integrity.
This game would be different from Mario Kart in that it would have much longer races and introduce a Ride Integrity system. This is a health bar put on each vehicle (how much is based on weight). The light-weight rides have 100%, while medium have up to 125%, and heavy have up to 150%. Each character can deal damage with an auto-attack (d-pad in the direction you want) on the Wii-Wheel, though items and specials hurt far worse. The strength, recharge, and reach of an attack is based on your character. The sheild can be used to stop damage to the ride (but has its own integrity of 100%.) Press the A button to deploy the sheild (can be held).
When ride integrity reaches 0, the damaged player auto-stops in place, and a pit crew (from their own game) comes to repair their vehicle (takes 10 seconds).
Here are the pit crews:
Ike/Roy/Marth- Soldiers/Mercenaries
Olimar- Pikmin
Fox/Falco/Krystal- Slippy Toad
Wolf- Robots (Not R.O.B.)
R.O.B.- A crew of R.O.B.s
Link- His "girlfriend" from Twilight Princess
Toon-Link- Tetra?
Peach/Luigi/Mario/Wario- A crew of toads
Bowser- A crew of Koopas
Yoshi- A crew of Yoshis
Donkey Kong/Diddy Kong- The other kongs
Any Poke'mon Character- A crew of the many... many Nurse whats her name
Pit- Palutena's army crew
Samus/Zero Suit Samus- A crew of Chozos or the Moth People from Metroid Prime 2
Zelda- Some soldiers
Sheik- Repairs her own ride.
Game & Watch- Some other Game & Watches.
Ganondorf- He's the king of evil.... he'll find something
Falcon- A pit crew (hes a racer... do I need to say more)
Meta-Knight- A crew of the Meta-Knights
Kirby- The split kirbys from Amazing Mirror
King D3- A crew of Waddle-Dees and Waddle Doos
The different crews are just for appearance. They have the same repair speed.
Controls: (Assuming Wii-Wheel) *Based off of Mario Kart Wii
1- Brake
2- Accelerate
B- Use item (including Final Smash)
A- Sheild
D-Pad- Auto-Attack (performed in the direction pressed, acts like a tilt)
Shake Wii-Wheel- Taunt
+ Button- Pause
I didn't include each characters ride because an above poster already did.