Language, history and curiosities in games.
Balance is not the same thing as fun.
Dollar for dollar, a roleplaying game is very nearly the most efficient entertainment you can buy.
The end of a game can be suspenseful, but your rules should not be.
Plenty of games are rock-solid mathematically and deader than Socrates when they’re played.
If you can get players talking like your game talks, then you’ve got them.