Pipe...

Pipe... is a paper note $$

Location
The note can be found on a corpse near the pipe in the Unusual Pipe random encounter.

Behind the scenes
This note and its related random encounter were created by level designer Zachary Wilson, who described it as "some nonsense [he] made at 8PM on a Wednesday at the end of the project when no one was looking," yet also called it his most successful contribution to gaming. Originally, "PIPE IS LIFE" was jokingly written in text so small it could barely be read, though this was changed by Steve Massey for the final release.