It has been discussed numerous times about spites where rides have been unexpectedly closed when visiting a new park. This topic is the exact opposite of that: What coasters did you expect to be closed when visiting the park but were actually open to riders? Same goes for children's coasters you expected to be denied but got on without trouble.
My best one for this recently would be Coaster Express at Parque Warner. While I had had the reports of how bad the ride is, I was still unhappy at the thought it would be down for it's retracking when I visited at the end of June. Luckily it was open and I got a few rides in! The ride is still rough though but can tell where they have retracked and is much smoother when not in a wheel seat.