In Sonic 3 there is a carnival level. At a certain point in the game there's this spin bouncing platform you need to move to get past. Many hours/days spent trying to get past that part.

Year later, in college I was thinking back on it and I looked it up, turns out it should have been much easier. Seeing your comment made me look it back up. Apparently it's called "the barrel of doom" and well known.

Before discovering GameFaqs, some games just ended at a certain part because you were lost.