General Lee
Boss Hog Caddie
Rosco Police Cruiser
Munster Mobile
Casket Racer (also from the Munsters)
Beverly Hillibillies Car
Robocop Crusier
Optimus Prime
National Lampoon's Wagon
Merth Mobile (Wayne's World)
Chitty Chitty Bang Bang
K.A.R.R. (Kitt's evil, cooler, twin)
Supernatural Impala
There are a LOT.
I wish a knew a team of game developers so I could get this off the ground. About all I would feel comfortable doing would be general direction/game concept design.
I would do it sort of like twisted Metal, where each car has a special offensive and defensive stat as well as a rechargeable special move. But in true Cannonball fashion, most of the specials would be guns and such, but rather shenanigan's. Like for the General Lee, the Duke Boys might get out and change all the road signs, the Lampoon Wagon would start falling apart, littering the road with obstacles, ect....
I'd like to do a true race across the country as well. Many games have attempted this, but they are always too shallow. I'd like to see one course per State of about 1-2 minutes in length which would make for a massive 1 1/2 hour race if you decide to go through every state, but could be as short as 10 min if you take the direct route. Racer's ahead of the pack can use their specials to block off routes, making those behind them take the long way around. Some specials would allow for short cuts, which would help those who are behind catch up. The game would use highway exits, similar to how Outrun does it to keep the stages dynamically loading.
And of course any sequel would take place in Europe.
It's one of those deals were legality would be an issue, but if the official game used generic cars and the game engine had an open-source scripting system it wouldn't matter.