Ranked Best to Worst:

NOTICE: 
Ken Kaneki -Centepede- may not allways spawn, if this happens restart the map or try a different map, you also need to be the one to kill him
[color=#cccccc][size=medium]Norma

Takes 30 seconds if you ignore all enemies and just run to the area. Its the only map that's the quickest however not ideal for getting shards and chunks. I also put in some tips when facing him!

More Arima guides:

Defeat CCG Reaper easily

[b][url=https://www.animeesports.com/Thread-How-to-easily-get-Kishou-Arima-Quinque-Shards-UPDATED--911]Kishou Arima -Quinque Sha

You can utilize this glitch to go outside of training area and see the world map freely to get familiar with it.
I reveal this because this glitch doesn't look like impacting the game badly.

Way 1. Using Unicorn Tank and Blueprint Tank
1. Put one Unicorn Hover Tank diagonally near the corner, and put blueprint car very close to that corner inside the Unicorn Hover Tank.
2. Get on Blueprint Car, and make it running mode.
3. While you don't move, press z to get off. By luck you will be out