Snaking in Mario Kart DS is probably one of the biggest examples of the "grain of salt" controversy mentioned in the opener.
There was also another variation to snaking, called the prolonged rocket boost glitch. If the player does a rocket boost from the start and then start snaking while the rocket boost is in effect, the player can effectively drive off road without slowing down as long as they keep using mini turbos without missing a beat.
Mario Kart Wii has one thing that is pretty game breaking; Shy Guy Beach and high rated off road bikes. Any bike that has an insane off road stat will have a huge advantage on this course since the course is mostly made up of water and no one will be able to keep up unless they use the same bikes or get lucky with items. While the course nor the bikes themselves are a game breaker, the combo of both are. People who spam Shy Guy Beach online usually are using bikes with high off road.
And Sherbet Land, since the whole course except for the cave counts as off road. So any bike with a high off road stat gets pretty much a huge advantage across the entire track due to being nearly immune to the slowdown effects of the icy surface. The offroad surface also makes the already ridiculous golden mushroom that much more valuable.
Grumble Volcano became infamous due to an exploit that allowed people to literally win in seconds because a certain spot on the track allows players to finish laps MUCH faster than they are supposed to. If someone keeps voting for this track online, there's a good chance they are picking it just to exploit the glitch. Less infamous, but still game-breaking glitches can be found in Mushroom Gorge and Wario's Gold Mine. Nintendo has tried rectifying this issue by auto-disconnecting those who try this.
Mario Kart 7 had one discovered on the Maka Wuhu track days after the game was released. Similar to the Grumble Volcano exploit, this glitch, if done right, lets the player skip more than half the track. Anyone who didn't abuse the same exploit online physically had zero chance of catching up to the people that used this trick. What makes this worse that Nintendo stated that they have no plans of fixing the problem, because they feel doing so may give some people an "unfair advantage".
In a case of Flip Flop of God being a positive thing, Nintendo patched the exploits so now they no longer work and the patch is required to play online. Maka Wuhu, Wuhu Loop, and GBA Bowser Castle 1 have been fixed. The exploit fixes only apply to online races, so it is still possible to cheat in single player mode and local multiplayer.
In Mario Kart 7, high off road stat karts and Neo Bowser City, since the wet surface/rain counts as off road. Seriously, just changing to use the Monster or Red Monster tyres will drop your time trial records on the level by about four seconds.
In Mario Kart 64, there are sevral design exploits, some involving the way Lakitu respawning you and others involving jumping over walls, that allow you to skip half or even the entirety of the course. In the North American release, they're Ascended Glitches, as the Player's Guide illustrates how to do these game-breaking shortcuts.
Diddy Kong Racing has the hidden character and time-trials referee, T.T. who has the highest acceleration and top speed along with decent handling, who made winning most races a breeze. The tradeoff is that this character is incredibly hard to unlock, but once you do, it's pretty much game over for the competition.
Gran Turismo 4 features unlockable cars as rewards for certain races, including Formula One cars (the number depending on what version you're playing). They're supposed to be there as Bragging Rights Reward, but one in particular can be attained without any effort whatsoever using a fully-upgraded Pike's Peak Escudo. Thanks to an upgraded HP equal to that of most motor torpedo boats, this can complete the course in question (a tedious 100-lap endurance race of a circular Indycar track) without ever changing tyres and while constantly scraping along a wall for the entire time. Proper application of sticky tape to a controller thus allows you to quickly 'earn' a car that easily wins every race in the game it's allowed to enter.
Any car in Gran Turismo 1 that can receive a stage 4 turbo is overpowered because you can easily reach over 700 horsepower without losing anything near the cost of an actual racecar. The Nissan Skyline Gtr variations and Mitsubishi Gto variations are the worst offenders, you can easily tune them to be just under 1000 horsepower and outmatch anything the game throws at you on the right tracks (A soft suspension, a track with roundish walls, and good tires are needed because running off of the track is quite easy when you have this much power; luckily you do not need to worry about vehicle damage).
The Pikes' Peak Escudo in Gran Turismo 2 is extremely overpowered despite being one of the few cars costing 2,000,000Cr. It has excellent grip and the most horse power of any car in the game. You could also argue that its little brother, The Pikes' Peak Cultis, and the Espace are also extremely overpowered because of their high power levels, however it is still easy to one up them with about 400,000 credits invested into a Skyline Gtr, a stage 4 turbo, racing slicks, full custom transmission, and whatever else you can fit.
Ditto in GT3. Despite being somewhat nerfed in its handing capabilities the aforementioned car already starts with a monster 980 horsepower and when it's upgraded with a stage 4 turbo it caps out at a earth cracking, ball busting, heart stopping 1884 horses. Rally races are especially easy, as spinning out does nothing when you can catch up in five seconds.
The Shelby Cobra Daytona Coupe is classified as a "G" (the catchall for slow old sports cars) ... despite being perfectly competitive in races against B-class supercars.
The TVR T440R is logged in C, but can clean the floor with many A-class cars.
Some areas in Burnout Paradise put a Stunt Runs challenge right next to some high cliff, allow you to rack up a ridiculous amount of score. When you are done with it, you can take out another car and spam the challenge again.
F-Zero has a few. X gave off quick speed boosts for grinding on the walls and GX had snaking (just like in Mario Kart DS) and spaceflying (which can shave off minutes of your time).
In Excite Bots, the Bat, which is both very maneuverable and very fast. The Spider as well.
There's also the Hummingbird which is pretty similar to the Bat.
Super Sonic in Sonic R is the fastest character, however he does have below average turning mechanics.
Wasn't Metal Knuckles proven to be "Higher Tier" than Super Sonic or something for his better handling, and being able to move faster horizontally during a glide than he falls?
Sonic Riders has Super Sonic, who has attributes of speed, flight, and power making him pretty much immune to obstacles and able to take any path on every race course as long as he doesn't run out of rings.
He eats through Rings so fast, however, that he's of a lower tier than regular Sonic. In Zero Gravity, he's considered more balanced because he can draw Rings into himself after a 60-Ring power-up.
Speaking of Sonic, Sonic and Sega All-Stars Racing Transformed has console mods, specifically ones like Shadow's. These racers end up having their speed and boosts ramped up to ridiculous levels, and on somewhat straight tracks, their horrible handling is trivialized. However, Sonic's Acceleration mod is just ridiculous. The acceleration isn't as high as other racers' mods, but it is enough to put him miles ahead of the competition in mere seconds thanks to his car's speed being higher than 3/4 of the roster. But the true game-breaking side is the fact that his handling is ridiculously high and thus allows him to speed around the 90-degree turns of Burning Depths or Chilly Castle with no difficulty. BUT, it doesn't end there. Thanks to what could be a Good Bad Bug, HIS BOOST STAT IS A LIE. MEANING HE CAN DRIFT OUT OF TURNS PERFECTLY. While it still is below average, thanks to the bug, he can accelerate and boost quick enough to trivialize it. There is a reason why many players online Rage Quit after racing Sonic, as his mods provide him the best coverage in the game.
And then there's console mod Tails, who boasts the same bug as Sonic, only applied to handling. Instead of being level 3 in terms of drift, he is actually around level 4 and a half, placing him on the level of Vyse, Shadow, and even AGES in terms of tiers thanks to his surprising speed, great boost, and decent acceleration. With this bug, a player on the psvita release got a TOP TEN SCORE in Time Attack at Seasonal Shrines thanks to Tails', a normally low tier character, bug.
In the Biker Mice from Mars SNES game, Vinnie has so many ways to get speed boosts that no one has the slightest chance to catch up wth him in 2 Players. First, his special turn allows him to do 90º turns instantly and gives him a boost when getting out of the turn. Second, his weapon is almost useless when actually attacking, but by pressing Y twice quickly, instead of jumping he gets a long boost. Then, all the characters get boosts by mashing the accel button at certain intervals, but Vinnie's come out faster. tl;dr: he can run the whole race under the effect of speed boosts. No one, NO ONE can catch up with him. And, ironically, the character select screen lists him with awesome acceleration and handling but the worst max speed out of all characters.
The Flatmobile of Flat Out 2. The fastest (beating even the rocket car, especially in acceleration), the strongest (can t-bone a school bus without taking much damage), with ridiculously grippy handling (why drift when your car can literally make that turn normally at the same speed?) and a brake that would throw the driver through the window instantly if the physics engine didn't require an actual collision to trigger the launch. And you don't have to unlock it to use it in multiplayer! Of course, since it's so fast, it takes substantial skill to drive, and as many newbies prove, its greatest nemesis is its own speed, smashing it against barriers at far faster than the damage system is designed for.
And now for a car that isn't very popular (half of players don't even bother driving it before meeting online) - Insetta (don't confuse with Insetta GT). FWD (cue ridiculous dodging), offroad (excellent grip on any surface), good speed and acceleration... and being almost THE toughest non-bonus car in the game, topped only by extra 0.3 armor of the Derby class' SUV. Good even at killing Flatmobiles! And while Flat is extra content, Insetta is a legal Race class vehicle.
LEGO Racers has a system where there's 4 different types of power-ups, and you can use up to three white bricks to build on to that power. If you max out a boost, you warp very, very, very far ahead of the course. If you keep repeating this, there is no way you can lose.
Except against Rocket Racer, who knows to do this himself.
The Piranha in Wipeout 2097. A hidden vehicle with extreme speed, "balanced" by its lack of weapons. Of course, when you get from 15th place to 1st in the first 10 seconds, who needs weapons?
In terms of weapons, the Quake. The only way to block it is to throw up a shield, and like other weapons, it screws up controls for a few seconds. Very helpful if you're in (or close to) last place and struggling to get a leg up on the competition.
In Wipeout Pure, it's possible to turn around and fire it backwards at incoming traffic. If the last place racer is also firing one at the same time, getting caught in the middle hurts as much as you would think.
Need for Speed Pro Street is a game featuring mostly regular tuners and hobby race cars, like the Escort Cosworth and Dodge Charger. Then came the McLaren F1 DLC.
The Mclaren F1's first appearance in II was a huge game breaker as well, in addition to being the fastest production car at the time, it also had the highest stats in all other attributes. And it was available from the beginning.
In Most Wanted 2012, the Everyday car class contains the Audi A1 Clubsport quattro, a pocket rocket with 496bhp and a 0-100km/h time of 3.7s.
Carbon also had the Nissan 240SX (but only in the Collector's Edition). Although an extremely difficult Challenge Series mission is requires to unlock the car, it is worth the effort. It is a Tier 1 Tuner with the highest stats of any Tier 1 vehicle. It is also the cheapest car in the game at a price of $20,000 (The Mazda RX-8 was at a price of $25,000). When fully upgraded, it can keep up with many Tier 3 vehicles, including Lamborghinis, Corvettes, and GT-Rs. The 240SX was, however, nerfed in later games.