If you have bombs, you can kill all the bokoblins with one bomb. Pull a bomb shortly before hitting the cutscene trigger (11 rolls from the entrance). After the cutscene, pick up the bomb, avoid the swings from the first pair of bokoblins, and then stand in the center and wait for the bomb to explode and kill all five. Alternatively, pull the bomb after hitting the cutscene trigger instead, then simply stand in place without doing anything until it explodes.
Slash the front two bokoblins 3 times, roll back twice, then wait for the 2nd set of bokoblins to come near you. Slash the 2nd set 3 times, then throw the Ball & Chain at all of them.
If you collect a rupee while charging a jumpstrike or during a jumpstrike, you will delay the text until you land (if during charge up, you will auto jumpstrike), Furthermore it also disables all triggers as the rupee text is queued up next.
Doing this skip requires yellow rupee text not to be cleared previously. Break the box in the left corner at the main doors and boomerang the rupee, then target above to delay the rupee, leaving time to roll. While the rupee is coming to you, roll to the very edge of the barrier 1 trigger (use the corner as a visual cue) and then start charging a jumpstrike. The rupee will hit you and you will auto jumpstrike over the trigger, allowing you to skip it. Later, after King Bulblin 4, savewarp to avoid hitting the barrier trigger on the way back, as it still exists.
This is recommended for RTA with a setup (see below) only if approaching the barrier without bombs or jumpstrike. Get on the wall on the left side of the castle and pull out the boomerang. Aim above the rectangular hedge and throw the boomerang. As it is coming back to you, do a Long Jump Attack to get on top of the hedge. From here you can open the door to the next area without hitting the barrier/cutscene trigger.
Go into the corner and do a vertical slash. Hold right to climb the ledge, then aim the boomerang so that the left line of the reticle overlaps the small gap in the foliage. The trick barely saves time for routes that have bombs. For routes that do not have bombs, this saves 5 seconds.
Climb in the corner of the ledge, then pull out the boomerang and tilt the camera up to push Link down the ledge slightly. Once Link can't get pushed anymore, align Link straight with the stairs, then turn 180. Target above the hedge, then LJA to make it over.
From the main entrance to the Hyrule Castle courtyard, head over to the left (GCN). Stand near the bush wall and lure a kargarok to come near you. Use an attack to knock the kargarok on the other side of the bush wall and target him with an area attack. Back up a bit, then use the the area attack to superjump over the bush wall and past the barrier.
Roll straight into the trigger for the barrier and skip the cutscene immediately, then roll back out before the barrier forms. On the way back, you can just walk inside the barrier wall as it is only one sided.
After King Bulblin is defeated there is a one frame window to backflip before Midna pops up. Press start during the backflip before landing and savewarp.
Alternatively, you can use Iron Boots instead of a backflip. Savewarp before Link touches the ground again.
This saves 6s.
This is by far the fastest and easiest way to skip this barrier. Jump attack towards the pillar on the right and mash start. You will skip the cutscene as soon as possible and because link is in the air he will not walk into the barrier. Then, head right to avoid entering the barrier accidentally.
This is slower than skipping the barrier entirely with a jump attack and is precise, so only use this as a backup. Head to the northeast and stand as far from the barrier as shown in the video, then put on the iron boots. Target a bokoblin and spin attack right as it's about to finish passing through the barrier. Without releasing target, walk towards the bokoblin until the A prompt to Finish appears, and then perform Ending Blow Moon Boots (EBMB) by pressing A while wearing the iron boots and then force unequipping the iron boots as soon as possible. This is precise because Link will be knocked back by the barrier if beginning the EBMB too close to it, the A prompt for ending blow will not appear unless Link is close enough to the bokoblin, and it's not possible to knock the bokoblin down closer to the barrier as letting it inside before spin attacking prevents it from being knocked out of the barrier at all. On top of that, Link will automatically untarget the downed bokoblin and instead target any upright bokoblins that approach inside the barrier.
This is slower than skipping the barrier entirely with a jump attack, so only use this as a backup in categories with helm splitter. Head over to the right side (GCN) and wait for the group of bokoblins to appear. Just as they enter the barrier, hit the first one with a shield attack and use the helm splitter to jump over the barrier. Link will sometimes hit the barrier during the helm splitter.
It is possible by standing on the very edge of the railing to clawshot the chandelier without needing to clawshot the closer one first, this is very hard to do fast as you have to be right on the edge and not recommended
With precise clawshot aim it is possible to reach the Chest and Switch on the SW platform of the central chamber without having to defeat the two Darknuts for access. By clawshotting to the southern edge of the NE chandelier, then lowering down slightly (see video), you will have between 1 and 3 vertical pixels to reach the southernmost chandelier. From there, adjusting to the SW edge will let you reach the SW chandelier after again lowering down a bit (not precise).
If you fail to skip the barrier in this room it is both faster and significantly easier to save warp and retry instead of fighting the horde of enemies.
Collecting a rupee that gives text while charging a jumpstrike will cause the jumpstrike to automatically release as a jump attack, disabling all triggers until after Link reaches the ground and the rupee text is displayed. This can be used to skip triggering the barrier that forms around the darknut. Use the ball & chain to break both suits of armor on the right, then stand on the part of the floor shown in the video below. Aim the boomerang just left of the column, then release it without targeting. Pull sword with B, target after the sword is out, then hold A to begin charging a jumpstrike before the rupee gets back to Link. Some strange side effects of this skip include the darknut music playing until Link exits the castle, an invisible damage barrier appearing near the middle of the room, and the darknut sometimes teleporting towards Link.
For the first phase sword roll towards him, rollstab and then slash him 4 times, then make him block again and do 6 slashes to knock off his armour. Now run into him to block the sword, wait for him to pull out his second sword and slash him twice. Now use B&C to finish him off with 3 hits. To get the perfect boomerang angle stand inside the diamond and aim towards the pillar, when camera pans back just throw the boomerang and it will hit the torch.
Once you skip the cutscene pull out a bomb and run towards the Dynalfos, when they notice you stutter for a while and then throw the bomb at them. They will run away from the bomb when it's on the floor after a while hence why you wait for a bit.
Alternatively you can just lure them to you and pull a bomb as soon as they start running towards you. When they are close, slash the bomb or blow it up by throwing the gale. This can be up to 0.3s faster than throwing the bomb, however there's a very rare occurrence where the Dynalfos will clip you out of bounds through the door, so do this method with caution.
Quickspin the Dynalfos, then stand right next to the left one. When they recover, chain stabs to kill both.
Run up to the Dynalfos and turn to the right. Perform neutral slashes 7 times, then quickspin to kill both.
Before getting to the Small Key chest you have to fight Aeralfos. The fastest way to do this includes using the Ball&Chain.
Enter the Barrier and skip the cutscene as soon as possible. Hold L and mash the Boomerang button to make Aeralfos shield and instantly clawshot him down.
While the clawshot is in the air, equip B&C over the boomerang and swing it. After you hit Arealfos 5 times, throw it in his direction - it will kill Aeralfos on its way back if done correctly.
As long as you don't stand on unstable blocks for too long you can just cut right across the room. To do this roll across and show in the video making sure you go diagonally so you don't stay on unstable blocks.
This only works for the last group of Lizalfos as they are closer together than the group below. Before spawning the barrier simply bomb-arrow the wall next to the right Lizalfos and it will kill both of them making the barrier disappear before you watched the cutscene to spawn it. This can be used in All Dungeons and 100%
Using the damage invincibility granted by getting hit by the barrier, it's possible to clip through onto the spinner track with a spinner attack, skipping the Dynalfos. Voiding out on the spinner tracks will respawn Link at the base of the tracks behind the Dynalfos and outside of the barrier trigger so you can safely go onto the tracks again.
It is possible to skip the final Darknut fight by clawshotting the lantern right next to the boss door in Hyrule Castle. Get off the spinner early and position yourself carefully right before the barrier trigger in the spot shown, then simply clawshot the lantern target by the door. Skip the cutscene and open the door. if you skip the cutscene too fast you will get knocked off by the barrier, so wait like a quarter second before skipping.
Original discovery video by DF here