$ (some command)
Over the course of a year I got periodic complaints that it "wasn't working" and I tried to find issues on my end and couldn't. One particularly vocal dev came to me directly and insisted it was broken, so I went on a shared session with him, it turns out they were pasting the "$" into the terminal causing it to say: "$: command not found."
That was the source of all the complaints, once I removed it, they stopped.