We bought a Monopoly knockoff called Bibleopoly and remade it into Demonopoly. The Biblical locations made it an amazingly fun thing to deface and rewrite.
Me and some other stoned people once combined Monopoly, Trivial Pursuit, and Axis & Allies to create a game where you could (a) get out of paying rent by answering a trivia question and (b) arm all your real estate holdings and invade other peoples' stuff.
It started off as "hey, let's play Monopoly!"
Then, somebody saw the Trivial Pursuit game in the closet and said "let's make a rule where you can get out of rent by answering a trivia question from the Trivial Pursuit cards!"
Then, somebody else said, "let's use the tanks and army guys from that Axis & Allies game and bring an element of ground acquisition into the mix!"
Combat rules for Axis & Allies applied to the combat pieces.
After you moved your Monopoly piece you could move your army guys one space in any direction and the tanks two spaces and "Chance", "Go Directly To Jail", etc. did not apply to them.
There was also a thing where if the owner of a piece of property was too retardedly high to notice somebody landing on it that the other players would work out some kind of "hush money" thing to not tell the guy somebody landed on his property.
Haven't smoked pot in years and board games are not as fun as they used to be.