What are some of the tangible things that programmers consider as their best friends?

In this question, Is it truly useful to work with more than one monitor?, people have said that a dual monitor setup is useful. Absolutely! For me, as a programmer; I cannot explain the joy of a second monitor referring to documentation while getting a mental picture of the solution from the code I’ve written so far.

My dual monitor is my best friend! As a programmer, what are a few other things that you hold near and dear, as a programmer?