Discovering hidden secrets is usually one of the most fun parts of a game - aside from beating up your enemies and getting sweet rewards.
Even when they aren't exactly well hidden, you still can't help but pat yourself on the back for a job well done when you find something that you didn't necessarily have to, but rather did because of a combo of your skills and desire to search every possible area and unlock every possible thing.
But sometimes, the things you get out of this kind of suck. Many items are a good idea in concept, but in practice turn out to be a lot less useful and cool than they first turned out to be. Even if said reward is powerful, it can quickly turn out to be useless in the wrong circumstances, or if you've finished enough of the game that there's no longer a real purpose for it.
While these secrets can be a fun surprise, you may find yourself wishing you'd never discovered them in the first place, because they ultimately fall a bit flat.