A Link to the Past - Chris Houlihan Secret RoomYou may not know it, but there is in fact a secret room room in the SNES version A Link to the Past (the room is not available in the Gameboy Advance version of A Link to the Past).
Chris Houlihan was a subscriber to an old magazine, Nintendo Power. Nintendo Power held a contest that Chris won, the prize being your own secret room in the (then) upcoming A Link to the Past. However, this room has been kept very secret, with many Zelda fans not even knowing about it.
Such a room was an awesome idea, even if asthetically speaking it doesn't seem that special. The layout of the room is like a normal cave, and there are rows of rupees lined on the ground for you to pick up. At the end of the room is a notice on the wall, stating that this is indeed Chris Houlihan's room and that you shouldn't tell anyone about it!
Getting Inside the Room
To access the room, load up your game and choose to start from the sanctuary. Sprint south (you will need the pegasus boots) until you have gone out of the sanctuary, and through the sanctuary's garden. Now run west, then once you have passed through a screen, go south into the wooded area (that is on the west side of the castle). Sprint through the forest quickly, then head east into the castle area. From there, sprint to the bush that covers the hole that you originally fell through at the start of the game, where you gained entry to the castle. If you managed to reach the hole fast enough, instead of the castle, you will fall into Chris' secret room.
If you want to try getting inside the room then this video ought to help, it shows the method that is described above. Inside the room you are treated to a bunch of rupees, and a secret message on the wall. It is by no means a big and fancy addition to the game, but it is a pretty cool piece of Zelda history.