The Periodic Table
Everybody has a certain item they just can't live without. Where would a doctor be without his or her stethoscope? How about Garfield without Pookie? Shmoop HQ wouldn't be the same without a continuous supply of burritos and cookies. For a chemist, that most essential thing is the periodic table.
The periodic table is the most important gizmo a chemist can possess. It's a toolbox, an encyclopedia, and a cheat sheet all rolled into one usually ginormous piece of paper. Seriously, has anyone ever seen a periodic table smaller than 5 by 4 feet?