In my family, we don’t play Scrabble/Bananagrams for points. I’m not even sure exactly how you’re supposed to win in Bananagrams. Instead, we play to make interesting words.
So, for instance, we have letter trading. “I almost have the letters for ‘toxin’- does anyone have an N they’re not using? Or a C, I could do ‘toxic’.” Or “Gah! Too many vowels! Anyone want an E or three?” “I guess I could use an E, would you like my D? Or maybe M?” And by the end of the game, when everyone’s down to their last tiles, it gets even looser. “Please, someone, take my G, I can’t do anything with it!”
After everyone is done, we read all the words in our grids, congratulating each other on the really good ones. I’m still really proud of ‘stegosaur’ and ‘chthonic’.
What games do you play by the ‘house rules’?
“House rules” are a requirement of any Monopoly game.
By general agreement, the people I usually play Trivial Pursuit with require that I complete two full wheels of pie pieces before I get to try and win. Yes, I play with them for social reasons. 
It’s not a board game, but my golf buddies and I have for years played golf with a modified set of rules. I’m actually excited to see that some of them are now being included in the proposed modernization of the rules.
Although I think that a lot of the reason that people think of Monopoly as being a game that takes forever and never finishes is too many house rules. For instance, the frequently used “money on free parking” means that way more money is injected into the game, meaning that it lasts far far longer.
Concept is supposed to be played like Charades/Pictionary/etc. with two teams competing against each other. I find it’s a lot more fun to play without keeping score and everyone just trying to guess what the clue is.