Keyes' pipe
From Halopedia, the Halo wiki
Keyes pipe being held on the Flood tentacle of the brain form.
Captain Keyes' Pipe can be found on the level Keyes, after the player reaches the Truth and Reconciliation's command center and taken the Captain's neural implants. If you look at one of the overhanding tentacles emanating from the Proto-Gravemind, you can find the pipe handing over the edge.
