Example video:
Spoiler:Example .pk3:
ZFighter.pk3
This map will spawn the player in a location where the ZFighting can be easily triggered.
Simply:
1. enable X/Y Billboard
2. open console and set NOTARGET
3. hug the wall immediately to the left of the player's spawn location
4. facing the line of pinky demons, move forward until the player's path is blocked by the rearmost demon, the next demon in line's sprites will begin to ZFight with the demon closest to the player.
This of course can also be replicated with the chaingunners as seen in the example video.