The Periodic Table of Middle Earth
Featuring characters from The Lord of the Rings and The Hobbit, I'd say The Periodic Table of Middle Earth would rank very close to the top of a list of Geekiest Items a Human Being Could Own. (I specified human being because if a dwarf, troll, or half-elf owned it, the poster would fall into a much lower echelon of geekiness, more in line with that of people who proudly display framed artwork of their family trees.)
LOTR Project's Emil Johansson has created this spin on the periodic table, incorporating, from left to right hobbits, men, half-elves and elves, orks/goblins/uruks, and, along the bottom, dwarves and trolls. He adds a special designation of "unknown" for Gothmog, which appears to correspond to copernicium or ununtrium in science's version of the table. Well, Emil, both of those elements are 100% unknown to me, so good choice.
Rounding out each character element's description are their birth and death dates in the top left corner, their "number" in the top right corner (I don't know what the significance or purpose of this is) and a small gold circle in the bottom left corner if the entity was a wearer of the One Ring.
Muchas danke to Nerd Approved.