According to the rules many people use for Monopoly, if you land on the Free Parking space, you don't just get to park there for free. You also get a cash windfall of $500 plus any fines players had to pay from Chance or Community Chest cards. However, that's never been an official rule of Monopoly (but it was one of five optional "House Rules" recently added to the game).
There is nothing in the original Monopoly rules that says a player who is in jail can't also collect rent when someone lands on one of their properties. But that is the law of the land if you follow the "Frozen Assets" rule, which is another one of the five "House Rules" that Monopoly added as an option in 2014. But if you go with the original rules, a player can simply hang out in prison and keep collecting cash.
In many games, rolling snake eyes is a very bad sign. However, if you roll two ones while playing with this unofficial Monopoly rule, you get to collect an extra $500. It's another optional rule that made the cut in 2014.
If there winds up being three tokens on three consecutive properties at the same time, this is called "3's a Crowd." In this situation, all three players get to collect an extra $500. This rule was nominated to be an optional Monopoly "House Rule" in 2014, but did not make the cut.
Official Monopoly rules, each player starts with $1500. But under the "Break the Bank" rule, half of all the money is piled in the middle of the board. Then when the game starts, the players each try to grab as much money as they can as quickly as possible. Monopoly considered to add this as an optional "House Rule," but did not...possibly because Monopoly was never intended to be a deadly contact sport.
Under the "Mum's The Word" rule, any player who's a mother automatically gets to get out of jail for free. It's not an official rule in Monopoly, or in the real world. Which is why you rarely see organized mom mobs causing mayhem out on the streets.
Some people play with a house rule known as "Take A Chance." When a player lands on Chance, they have the option of picking a Chance card, or doing nothing. However, if you don't take the card, you'll never know if you would have been arrested for house repairs, or made some extra money by coming in second place in a beauty contest.
If you draw from the Community Chest, you have a choice under this house rule. Instead of accepting the card, you can auction it to any player at any price. However, you don't get to look at the card before selling, so you might end up getting rid of this very fortunate bank error that would certainly never occur in the real world.
Under this rule, a player who lands on Go does not get to collect $400. Instead, they have a choice between either taking the $200, or advancing to literally any other spot on the board. And if you're playing while using the "Free Parking, Fast Cash" rule, that might be the spot to pick.
Here's a complicated one. Under this rule that's not actually a rule, one player per game may, at any time, declare voluntary bankruptcy. At this point, they return all their properties and money to the bank, and in return receive $800 and all the purple and brown properties. If anyone owns those properties, the bank compensates for seizing their assets by offering money for the properties, houses and hotels. It's only too bad that you're not allowed to do this in real life.
One Monopoly rule that is definitely real is the one where, if you roll a double, you get to roll again. However, if you land on a property on that first roll, you still have to pay rent. But under some house rules, the double roll is not considered an "overnight stay," so since you are travelling, you don't have to pay.
Instead of waiting for every player except for one to go bankrupt, it's often much easier to play a timed game. Just set a timer for however long you want to play, and then each player counts up their money when time is up. Of course, if you didn't have rules like "Free Parking, Fast Money," players would go bankrupt sooner and the typical game wouldn't keep going for 5-10 hours.