Ganon's Tower Clip
Similar to the Hera Clip , it is possible to clip into Ganon's Tower without opening the entrance.
If you have the boots and the hookshot, it's very easy.
Line up with the top of the area where you are. Hold your sword then Hookdash.
Then move left in the edge until you can't.
Then fall with, after the fall press to get unstuck (you will see link moving left), after than you can hookdash to swordclimb up.
If you don't have the Hookshot, you can still do it with multiple inputs at the same vertical position.
Pinkus made a guide found here.