When you progress normally through Twilight Princess, after you beat Lakebed Temple and enter the portal, Midna loses all of her powers due to her encounter with Zant. But when it became possible to beat Lakebed Temple without Zora Armor, it also became possible to beat Lakebed Temple BEFORE Laranyu Twilight. This may lead to what might be one of the biggest sequence breaks in the game.
After beating Lakebed Temple, the encounter with Zant cutscene appears to start in the twilight, only to abruptly end itself as if it was skipped. The game continues by playing the following cutscene where the Spirit of Light warps Link to North Hyrule Field, except it takes place in the twilight.
When the game resumes, it is in a mesh of different states all at the same time. Since the previous cutscene would have taken place in the normal world, Epona will load if she was in Hyrule Field. Because Midna is injured, the game loads the enemy set for Midna's Desperate Hour, which is completely devoid of enemies outside of the area fenced in by the Midna Text. And because Laranyu is still in twilight, the twilight effect partially loads, giving Hyrule Field the "Dark Twilight" appearance. For whatever reason though, the Midna Text no longer stops you from leaving the area.
If you jump out of bounds while still inside Laranyu Province, the game will permanently override the Midna's Desperate Hour state in North Hyrule (except in Hyrule Castle Town), and you'll respawn inside the normal twilight. If you jump Out of Bounds or get Gameover outside of Laranyu Province but don't leave Hyrule Field map, the "Dark Twilight" will be cleared, and time will progress normally (time is normally locked to night at this point), but Midna's Desperate Hour enemy set will still be loaded. Also, the twilight barrier that would appear around Laranyu Province will be gone.
The most important effect though is that while Midna still loses most of her powers as she would normally, she still retains the ability to warp. This could turn out to be incredibly useful, as the ability warp allows you to be able to return from Gerudo Desert and enter the City in the Sky before meeting Zelda, and before the impenetrable Ganon Barrier around Hyrule Castle is raised. Furthermore Hyrule Castle. If a way into Hyrule Castle early was discovered, it would lead to the complete skip of Snowpeak Ruins and the Palace of Twilight.
With the somewhat recently discovered bomb boosts in Hyrule Castle, even skipping Arbiter's Grounds and City in the Sky and with them Spinner and Double Clawshots would be possible, resulting in the biggest sequence break in the run by far.