There are 7 coins hidden throughout the Tower area.

Comedians David Cross and Brian Posehn were asked by Bungie to write dialogue for the character Ghost. The two were flown to the studio and there they wrote a series of riffy one-liners with some lines that were self-reverential for the character. However, none of the dialogue was used for the game and the character was instead kept as monotone.

It is possible for a player to kill themselves by shooting themselves in the foot while in knee-deep water.

The armor shader named 18237496-64703388 is named after the RGB color codes for blue and yellow. Additionally, if these numbers are entered into a GPS (longitude-latitude) it will show a location in Sweden, a country that has both blue and yellow as the colors of its national flag.

The Armor, Heart of the Praxic Fire, has references to the Dark Souls character Solaire of Astora:
One of the upgrades is titled "PRAISE THE SUN". The upgrade's icon also resembles the emote of the same phrase.
The description, "In that last moment she seemed as wholly luminescent as the Sun, and I wished to be so brave." is likely a reference to Solaire's line, "The Sun is a wondrous body like a magnificent father. If only I could be could so grossly incandescent."