I hate it when I spend all my money to build a rollercoaster, and, after I test it, it's too intense for the guest to ride. I tried to build a mega coaster in one of my parks that had an itense level of 28!!! It had a lot of spiraling drops, and a 95 mph speed.
I straightened a few turns here and there, and removed a few of the zig-zag speed turns I put in, and got the coaster down to a 10. Guests will ride it, but it's popularity is low. Even though it is a great looking coaster!
Another ride it seems hard to build, are mad mouse coasters. No mater how great they look, the guest don't seem to like them. I have one mad mouse with an excitement rating of 9, and, only a few guest like it. While one of my smaller coasters with a 6 excitement rating is loved by hundreds?
Very strange guests I guess!