No, this is Groo (at least to me).
“And now, Groo does what Groo does best!”
CHEESE WHIZ
The ham radio license is awfully nerdy…not to mention the horded radios…
I have a pretty good collection of Motorola two-way radio encryption gear, too.
The 3.5 watt argon laser in the basement doesn’t serve any real purpose.
Same for the vintage BMX bike.
Nerdiest of all may be the EE diploma…
I’ve also got a couple of business cards from The Bone Room, and a “simulated nuclear fuel pellet” from the Nuclear Energy Institute.
That and my Amelie Poulin and Roland the Headless Thompson Gunner figures. Hand-crafted, too.
I’ve got about 17 or 18 of things other people listed. I’m not sure what my nerdiest is, but it’s probably due to volume/completeness. such as:
My near-complete collection of Ravenloft D&D products (missing 1 module, 2 PC games, the dicepouch and about a dozen minatiatures)
My near-complete collection of Highlander: The Trading Card Game cards
Massive amounts of Star Wars figures don’t count, do they?
Life-size cardboard (and half-lifesize lego) yoda seem downright pedestrian.
Autographs are a dime a dozen (Ray Park, Nichelle Nichols, Rene Auberjonois, Sam Kieth, Douglas Adams…)
What about a homemade The Maxx costume?
12"x18" Cross-stitch of the Fellowship of the Ring movie poster?
Is it… this rabbit here? (If you follow this link, be sure to check out the “Action Shots”!)
Can I say for the record that I am buying one? 
It’s Cheese Dip, you mendicant! 
(And don’t even ask about “mulch”…)
I’ve got a lot of nerdy things. I have no idea which is nerdiest:
A collection slide rules (I used a slide rule up to my junior year of college)
A DigiComp mechanical computer
A Cosmorama home planetarium
A whole shelf of science fiction and fantasy reference books (in addition to a huge number of books)
An old copy of the CRC “bible” that’s so small it really does look like a bible
A Brass Rat
An old working Commodore 2001 computer with the “Chiclet” keybboard and integrated cassette tape drive
The old manuals from the Gilbert chemistry sets I had as a kid
An Erector set
An Opaque Projector that I built myself as a kid
The First Fossil I ever Found
My eight grade Science Fair Project (including the cardboard presentation boards)
All my old Boy Scout patches, badges, medals (in their original cases) and neckerchief slides
Is a lava lamp so nerdy it’s cool, or is it just nerdy? Or just cool? Anyhoo, I gots one.
And my cell phone rings to the “Fellowship” theme from LOTR:FOTR.
I have a Klein bottle, and a piece of Trinitite. They are on my desk. (For those with SDMB old timer credentials, these, and the piece of petrified turtle crap are the three objects that no one bothered to remote view, back in the day.)
Tris
“In my opinion, there’s nothing in this world, Beats a '52 Vincent, and a red headed girl.” ~ Richard Thompson ~
The Sage’s dog hates his name.
Speaking of Groo, I have the issue #1 from Epic Comics and the collected *Groo Chronicles *
-
All of Rush’s recordings, save Caress of Steel (somewhat hard to find, that)
-
A souvenir Rush wallet from the Vapor Trails tour
-
A souvenir Rush keychain from the 30th Anniversary tour (with the logo from Hemispheres)
-
Ringwraith and Gollum “action figures”
-
The Middle Earth Atlas
-
The first edition Silmarillion with the groovy fold-out map
-
Photo Companion books for FOTR and TTT
-
Various Marvin the Martian objects
-
An assortment of Star Trek and Star Wars tree ornaments (I’ve got the Gallileo 7 with Spock’s “Happy Holidays” greeting on it! WOOT!)
Hobbit boardgame circa 1970s
Microscopic Space Fleet
Fluff
Peril Sensitive Sunglasses
Button bearing the words “Don’t Panic” in large, friendly letters
Orders for the demolition of Arthur Dent’s house
Orders for the demolition of Earth
Various vacuum tubes
Vacuum tube tester
1940’s multimeter labeled in French
Rankin Bass Hobbit record
Rankin Bass ROTK record
A suit of techno knight armor made from junk. The latest version has a hawk helmet and large mylar wings.
Lord of the Rings version of Monopoly.
2 Tron beach towels
A translucent staff. Tap the base on the floor and the LEDs inside the staff flash.
A shuttlepod Magellan 3.5 disk holder.
How does my Marvin the Martian PEZ dispenser rate? It’s battery powered!
IMO
The only Pez dispenser which count as nerdy are the following-
The giant ones that dispense whole packs of Pez instead of a single candy.
Any of the Universal Studios Monsters
The psychedelic hand holding an eyeball released during the sixties’
The original golden glow, and silver glow (made to resemble cigarette lighters)
I apologize completely and unreservedly for that apostrophe. I have no idea what happened. It has not been a good week for me.
Back To The OP
The Mysterious Green Substance- When I used a newly-acquired copy of the Golden Book Of Chemistry to electrolyze water, I ended up with a green precipitate. Cuprous Oxide? Cupric Oxide? I don’t know.
Hmm, Sci-Fi-ish Looney Toon and Battery Powered. This sounds like it Qualifies as a geek Gadget to me.
Jim
IMO
To be nerdy an item must be-
Esoteric in appeal
Shunned by the general populace
Dificult to obtain- ownership thus representing a significant outlay of time, effort, and possibly money.
EG The phasers, communicators, and tricorders owned by so many of us cannot be the supremely nerdesque item of this thread as they are common and easy to get. An actual prop used in an episode or film would be rare and hard to get, and thus far nerdier.