Out-of-Bounds Techniques

Rope Dart
Currently, the rope dart can be used to go OOB. This can involve using the rope dart right before you hit a death trigger, with the iframes allowing you to pass through the trigger. In almost all cases this will cause you to be stuck OOB causing a softlock. However, it can also be used in more useful ways to clip into ceilings.

Hook Clip
Alternating Jump/Rope Dart in rhythm can allow you to clip easily through some ceiling

Here's a nice montage of some: video

Wall Jumping
A precise wall jumping (near the bottom of the tile) allows you to clip through the ceiling and do some minor/major skips.

You'll not always be able to clip through ceilings since it depends on the placement of the level collisions

1 Tile clip
The wall is only 1 tile high.

If the ceiling is more than 1 tile width you can hold against the wall.

Otherwise, you will need to do a backward clip (hold away from the wall while you're in the air and then hold against the wall just before wall jumping)

2 Tiles clip
The wall is 2 tiles high or more

The setup is pretty much the same than the 1 tile clips but it can be harder since you must wall jump off the uppermost tile without wall jumping off the lower tiles

Shop Death Abuse
This trick is only available once you are able to go at the portal room inside the shop.

In order to do this trick you need to go at the leftmost of the room and do a Hook Clip or a Backward 1 Tile Clip and then duck to die once in the wall.

You'll respawn in the regular level while the game will still think you're in the shop so a lot of content will not be loaded. Example

Autumn Hills

 * First Seal Enter
 * First Seal Exit
 * Boss Skip

Catacombs

 * Level Skip

Bamboo Creek

 * Forlorn Clip 8bit
 * Forlorn Clip 16bit
 * [Forlorn OOB]
 * TurtleMen Ranged Door
 * Wanderer
 * Platform Elevator

Howling Grotto

 * Small Grotto Clips
 * Sunken Clip

Quillshroon Marsh

 * Small Clips
 * First Seal
 * Last room

Searing Crags

 * Music Note
 * Small Crag Clips
 * Seal 1
 * Seal 1 Any%
 * 3 Graplou Thingy
 * Boucing Doggo
 * Spikes
 * Last Tall Room

Glacial Peak

 * Small Peak Skips

Tower of Time

 * First Half
 * [Wall Crushers]
 * Vertical Lasers
 * [Wind]
 * Wind to Swing
 * Swing
 * Boss Skip

Cloud Ruins

 * First island ~15s
 * Seal 4

Underworld

 * Small Clip

Riviere Turquoise

 * Matriarch 1 cycle ~20s

Elemental Skylands

 * [Air Island]
 * Earth Island
 * Water Island Fast
 * Water Island Slow
 * Fire Island
 * Small Fire island

Sunken Shrine

 * [Sun Crest]
 * Moon Crest
 * Light Tabi (requires 7 health and dmg reduction)

Music Box

 * Level Skip
 * Dimension Puzzle
 * Steam
 * Elevator
 * 8bit Path Boss