Inspired by the mention of Handwavium in class, and also influenced by the Week Six presence of Michael Swanwick and his nifty Periodic Table of Science Fiction, several of us, most notably S. Hutson Blount, Assistant Lab Technician, started labeling the Clarion West elements:

Addendium
A stand-in ending, e.g. "Everyone gets hits by a truck. The end." Among the most common of the Clarion West elements. Same Group as Underwritton.

Ambigumony
Commonly found near the ends of stories--or is it?

Explainium
The fundamental element in Exposition molecules. Same Group as Telline. Explodes when brought into contact with Showium.

Dulline
A heavy, colorless gas. Would be in the same Group as Tedium and Boron, if those weren't already real things.

Genrium
Toxic element capable of contaminating most other elements by exposure. Use severely restricted in most markets.

Hardon
A random sex scene, particularly one in which the female(s) don't actually get off.

Homagium
Close chemical relative of Borrowlium and Thievium, which mimics the cool properties of all the other elements, often without attribution.

Horriblethingon
Frequently diatomic, and always horrible. Same Group as Squickine.

Literium
Especially pretentious element in high demand, yet of low market value.

Niftigen
Contains pleasing properties of many kinds. Often found in compound with Homagium.

Overreachium
Extremely ambitious substance which can cause uncontrolled story growth.

Paradoxium
Often found in time-travel uses; unstable isotopes of Paradoxium will eventually decay to become more Paradoxium.

Redirectgen
Has extreme attention-getting properties, often used to divert focus from less stable elements. Same Group as Distractgen and Miscuvium.

Retron
Golden-Age element, with properties more innocent, exciting, and sexist than other elements. Same Group as Nostalgium and Campium.

Sirenium
Water-soluble element used in mermaid formation.

Unobtainium
Frictionless, mass-less, and indestructible -- in high concentrations, even invisible. Related to Handwavium.

Zepplon
A pleasant smelling gas, often used to keep a flagging story aloft. Most every story benefits from the presence of Zepplon. Same Group as Monkine.

Zombine
Essential element in all zombie-making catalysts, e.g. alien virus, bioengineered virus, television, voodoo. Same Group as Undeadium.

Comments on, since there are surely more to be added...if nothing else, at least Texasholdium, Viagron, and Hornyhousewivescheatine.