Me and my brother spent last night discussing a really interesting concept for a game.
Mad Max as a multiplayer, class-based videogame.
There'd be four classes. Leapers, Gunners, Drivers, and Engineers. Leapers are adept at parkour and can leap from car to car with ease, and are generally agile. Gunners are good with guns and can fire steadily even while on top of a car. Drivers are excellent stunt drivers and can keep the car steady even when it should spin out. Engineers can repair the car and can cause oil slicks and other ways of impeding the other drivers. They can do each other's jobs, but they don't do them as well.
The main mode would be two teams on an open road trying to take the other out by any means possible. Cars would be assigned like squads in Battlefield: you could bring your own car, or join in by getting in a car. Each car would be arranged in classes: very light being motorcycles and dune buggies, light being sports cars, medium being station wagons, heavy being SUVs and hummers, and very heavy being trucks and APCs. The team's amount of cars would be limited by weight: you could have a horde of motorcycles, or a single truck surrounded by a few sports cars protecting it.
The game itself would be like TF2 on wheels. The cars would have to handle very well, and it'd play in the first person. Everything would be authentic, though not exactly realistic: this is a stunt filled car film from the 70s/80s rather then an actual post-apocalyptic scenario. Cars would flip, get knocked off the road, smash into other cars and end up in a horrific mangling. Complicating things would be the fact that players can get out of their cars and jump from car to car like in the climatic finale of Mad Max 2. It should be possible to have a fist-fight occur on top of a truck that's about to go on two wheels and flip.
Another thing would be modification. You can choose to modify the cars before the match with a lot of options. You can make even station wagons tanks, and trucks really fast with nitro. You can also add turrets and catapults. You aren't limited to cars either. It's less like TF2 and more like Brink when customizing your character. You can choose your gender, facial features, and hair style. Clothing is also there as well. Your character can also learn their own skills and traits, such as the ability to have better balance when running around on cars, or the ability to heal your teammates inbetween matches.
You can also modify your own weapons and make them. One of the cheaper ways to make a flamethrower is to simply combine a bottle of alcohol and a zippo lighter which will allow you to gulp down a bottle of jack and blow fire into the enemy's faces. You could also have the option to pee on your own melee weapons in order to infect your enemies, like Jarate but with everything.
The teams would consist of four seperate factions with their own starting equipment and bonuses. The Bandits are the pragmatic but still dangerous robbers and cutthroats of the post-apocalyptic world, who are generally the "jack of all trades" faction with generally okay weapons and no particular disadvantages or bonuses to the classes. The Psychos are utterly insane bezerkers who are on so many drugs that they have pretty much snapped in half, and have more health and a focus on melee weaponry and a focus on motorbikes. The Cops are the last remnants of the police and military forces after the apocalypse, and have much better firearms (with rarer ammo) with a focus on hummers and cop cars firmly in the medium-heavy range. The Tribals are a collection of tribes who decorate their cars and weapons religiously, and have a focus on unconventional weaponry and cars such as bows and trucks. However, each faction doesn't have it's own leveling system of weapons: the majority of weapons/vehicles after the initial starters can be generally used by anyone.
From this starting position, a lot could be done with the formula. New maps (Imagine having to drive crazily and fight at the same time when you're driving along mountain cliffsides), new gamemodes (Defend the Truck? Chicken? Racing?) and new characters and weapons.