This is the list of glitches; you can not use any of these in a glitchless run of the game.

Corner Clipping / Wall Zipping - Glitch You clip into a wall using irregular behavior; therefore, this is a glitch.

Emote Clipping - Glitch This includes Dance Clipping and Laugh Clipping which clip through a wall using irregular behavior; therefore, this is a glitch.

Buffering - Glitch This includes Lag Clips and Lag Laugh Clipping where you lag your game to get an advantage using irregular behavior; therefore, this is a glitch.

Flicking - Glitch Flicking your camera isn't, but doing it for a reason is a glitch: such as in Wall Hopping and Ladder Flicking both use Flicking to clip into a wall for a short period of time to jump off of the wall; therefore, this is a glitch.

High Jumping - Glitch High Jumping is performed by running up to a wall and immediately jumping; extra height is gained by your character clipping into the wall and getting instantly pushed out, exceeding the jump limit; therefore, this is a glitch.

I have to add a note that Melee Movement is not a glitch, as it is intended by the creators.