We have Wambam Family House Rules for Scattergories. Honestly, I can't remember right now what's different about our rules versus the official rules. I just know that I've played with other people and they've WTF'd me lol.
We do the free parking money, too. But we don't start it off with anything - we just add as we go along.
Are trading and bargaining part of the official Monopoly rules? I think they're not. And most of our Monopoly fun came after most of the properties had been purchased and we started making trades. My older sister cheated us younger kids soooo many times before my parents stepped in and started acting as our financial advisers and telling us why her trades were terrible ideas.
Free Parking is the worst house rule in Monopoly. It's pretty much a guarantee that instead of 4 hours (which is already way too long), you'll be playing for 7.
H and I sometimes play Scrabble without scoring the special spaces.
The original rules of Munchkin specified cheating was acceptable and we houseruled that out. I believe that rule was removed in the newer versions though.
In Uno we play where you can stack Draw 2s, Draw 4s, and skips and reverses. To screw someone over and save yourself
This is always allowed in two-person play. A reverse/draw card is essentially a skip when you're playing one-on-one, so you can stack them and annihilate! It's such a rush!
When playing Mexican Train (dominoes) with my parents, we have the Uno rule that when you're down to your last domino, you have to call "UNO!" Or else you have to pick up more.
I'm basing this off of the rules that came with our Mexican train domino set, which didn't allow for this, but you can play on others' trains if their marker is in use.