Pokemon Mystery Dungeon: Gates to Infinity -
I found a red door(which I had a key to), so I opened it. I found a treasure chest, and a pokemon guarding the chest. It took 2 reviver seeds(one on me and the other on an AI-controlled teammate), but I got it without being able to even harm the pokemon guarding the chest. That's right, the team I had assembled couldn't even damage the dang thing.