These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Settlers of Catan
Game Breaker: The Aqueduct in the Cities & Knights expansion allows players to have production even when their resource numbers aren't rolled. Players who get this early usually have a huge advantage.
Scrub: Since settlements must be at least two vertices apart, placing a settlement an odd number of vertices away from another will reduce the number of legal build-spots for everyone, sometimes sharply. Sometimes Scrubs arise who insist that this shouldn't be legal, and everyone should be required to place settlements for maximum density.