Keyes' pipe

Keyes' pipe was a gift from his grandfather, likely a corncob pipe, used by the Captain to smoke tobacco. Despite being against regulations, Keyes kept it with him most times, using it to aid concentration - not neccessarily by smoking it, but at least holding it. By the 26th Century, pipes like his had become antiquated, replaced by cigars and cigarettes.

Keyes' Pipe can be found in two missions - in Pillar of Autumn, Keyes removes his pipe from his mouth to address the Master Chief in the second cutscene. The pipe can later on 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 the player looks at one of the overhanging tentacles emanating from the Proto-Gravemind, they can find the pipe hanging over the edge.

Keyes smoked his pipe when he was nervous, though it was against the rules. He smoked it on the bridge once or twice. He kept his pipe with him in his pocket.

Unconfirmed, but the player is supposed to see a small pillar of smoke coming from the pipe if the player plays through the level on Legendary. Only on the level Keyes. Not the level Pillar of Autumn. This is still Unconfirmed.

Also Unconfirmed- Martin Ritter (screen name Reaper) spotted the Marathon symbol on the pipe. It can be seen as Keyes gestures toward the view screen with the pipe. It is located on the front of the bowl of the pipe. Mr. Ritter would appreciate confirmation by other Halo fans.