Zombie Glitch

Requirements
None for the glitch itself, but the setup requires:
 * Shortcut
 * Waystones
 * Access to spikes

How to perform
The setup is as follows:
 * 1) Get to low HP (enough that spike damage will kill you)
 * 2) Set a shortcut with the waystone item on it
 * 3) Fall towards spikes, hit the shortcut button just before hitting them
 * 4) Pick the waystone shortcut. If timed correctly, you will take damage and go to 0 HP during the waystone animation.
 * 5) You will appear back in town with 0 HP. You are now unkillable.

Properties
Dying on the same frame as an animation that locks controls will leave you alive at 0 HP. In this state you cannot die, collect powerups (except in speedrun mode), open the pause menu, open the map, or open the shortcut menu. Any healing will immediately end the zombie state. Any powerups collected while in the state, including HP up will apply as soon as the state ends.

Confirmed animations that can cause the glitch:

 * Collecting a shard for the first time (animations on)
 * Using a waystone from a shortcut
 * Inverting gravity
 * Dimension Shift

Unconfirmed animations that might cause it:
It seems to be possible to take damage during the first few frames of an animation by spikes only. This can be used to set up the glitch without frame-perfect inputs (example below).
 * Picking up a powerup
 * Leveling up
 * Entering a cutscene (somehow)
 * Pausing (reportedly you will have 0 HP on the pause screen)

Videos:
Setup using shortcut waystone and spikes

Accidental activation of the glitch with inverter

Accidental activation of the glitch with dimension shift