Thing-O-Meter

A speedometer measures how fast you go, a radiometer measures the radiant flux of electromagnetic radiation, and the Thing-O-Meter measures everything else.

Commonly seen as the Laugh-O-Meter or Applause-O-Meter, which is based on the Clap-O-Meter used in old game shows. There are thousands of variations, though—Suck-O-Meter, Creep-O-Meter, Love-O-Meter, Sarcasm-O-Meter, basically Whatever-You-Want-O-Meter.

They're usually not very reliable, as their indicators are prone to going off-scale or even breaking. They generally measure things on an Abstract Scale.

Though popularized by game shows and the like, this trope is Older Than Radio at the very least: William Hogarth's 1727 satirical engraving Masquerade Ticket features "a pair of lecherometers, showing the company's inclinations as they approach 'em."

Not to be confused with any of the meters used in games (like Karma Meter). Compare Thing-O-Matic, The Little Detecto, Everything Sensor and 20% More Awesome.

Examples of Thing-O-Meter include:

Advertising

Nicorette's "Suck-O-Meter" ads (the page pic is one such ad).

Film

Ghostbusters. When the team goes after the library ghost Egon Spengler has a meter that reads PKE (Psycho Kinetic Energy) valences, which are apparently given off by ghosts. It's the one that has the "arms" go up when the PKE increases.
The movie That Thing You Do had an applause-o-meter that determined the winner of a band contest.
In Cloudy with a Chance of Meatballs, the FLDSMDFR has a dangeometer to warn Flint if the food is going to over-mutate.
Men In Black. Not a literal device, but

Jay: This definitely rates about a 9.0 on my weird-shit-o-meter.

Literature

Discworld
- The thaumometer, which measures a magical field in "thaums". Mind you, this is just a perfectly sensible piece of equipment for a wizard on a world run by magic.
- Moving Pictures has the resograph, a device designed by a wizard named Riktor the Tinkerer to measure changes in the fabric of reality. On the Discworld, said fabric is a lot more flexible thanks to the power of belief and the Theory of Narrative Causality.

Live-Action TV

Queen for a Day's Applause Meter - Trope Maker if not Ur Example.
Canadian teen talk show Jonovision had an applause-o-meter to determine how much of the audience agreed with the topic du jour.
On Frasier, Niles snarks that the psychic debunker they've invited over will be bringing a "ghost-oh-meter" (hard "o"). Daphne rejoins that it's called a "ghost-ah-meter" (soft "o").
In the Mystery Science Theater 3000 episode featuring Angel's Revenge, Tom Servo invents a Shame-O-Meter (pronounced "shuh-MAH-meh-ter") to measure the shame the actors in the film are feeling.
- In another episode, Joel invents the Steve-O-Meter, which measures whether a given idea has already been thought up by Steve Allen.
Saved by the Bell had a Love-O-Meter at The Max.
An Ascendometer is a self-contained, portable unit from the Stargate Verse used to analyze neural activity in the brain. This allows people to judge how close to ascension someone is.
- Originally found on P3X-584 in SG-1, the device was named as such by Cameron Mitchell, leaving Samantha Carter wishing she had thought of it first.
- Assumably the very same device was used in Atlantis when they were monitoring how near to ascension Dr. Rodney McKay was during the events of 'The Tao of Rodney'.

The Summarize Proust Competition on Monty Python's Flying Circus uses a graph gauge to determine who can summarize Marcel Proust's A La Recherhe du Temps Perdu best. (No one can, so the prize goes to the girl with the biggest tits.)

Professional Wrestling

During his reign as WWE Intercontinental Champion, Santino Marella would rate himself against the longest-reigning IC champ in history, The Honky Tonk Man, using the "Honk-A-Meter".

Radio

On an episode of I'm Sorry I Haven't a Clue, the round of Mornington Crescent ended with Humph announcing "According to our clapometer, Tim is the winner". Barry Cryer then added "Report to the clinic immediately".

Web Comics

How do WebcomicHomestuck trolls know how effective their trolling is? Kanaya uses the "Flighty Broads and Their Snarky Horseshitometer" in an exchange with Rose. It ends up exploding (after Rose goes Off the Rails and blows up her gate), because it simply couldn't take that much horseshit.
- You can't forget the Prankster's Gambit.

Web Original

RationalWiki's Irony Meter. Irony Meters are often mentioned on FSTDT, usually in in a Readings Are Off the Scale Explosive Instrumentation way.
In Sonic the Hedgehog 2 Special Edition, a clap-o-meter is used during the Clap Your Hands If You Believe segment.
Cybershell's Let's Play of the Genesis Sonic games started each zone with a map and an overview of the enemies in the zone, each rated on how annoying it was using a "Cunt-o-meter".

Western Animation

A laugh-o-meter features prominently in a the Batman: The Animated Series episode "Almost Got 'Im," where Joker rigs one up to an electric chair, straps Batman to it, and lets laughing gas leak into a studio audience.
The Care Bears have, of course, the Caring Meter, which monitors how much caring is going around on Earth.
Clone High's official voting system for student council president is an applause-o-meter. This meant that, in a heated competition between Abe Lincoln and JFK for the presidency, the winner was a random puppy who wandered on stage.
On Futurama Professor Farnsworth once pulled out a "cool-o-meter" which apparently measured coolness in MegaFonzies.
- On another occasion, he pulled out a "Doom-o-meter" that measures just how doomed something is, in Milidooms. Of course, 1000 Milidooms = 1 Doom.
The Simpsons: Professor Frink's Sarcasm Detector.

Lyndsey Nagle: Do I detect a note of sarcasm?
Frink: With sarcasm detector Are you kidding? This baby is off the charts, mm-hai.
Comic Book Guy: A sarcasm detector, that's a really useful invention. [Sarcasm detector explodes]

- Frink has also brought his Frog-Exaggerator to Loch Ness, thinking he had brought his Monster-o-meter.
- Also from The Simpsons, in the "spinoff" The Lovematic Grandpa, wherein Grandpa Simpson dies and is reincarnated as a love testing machine at Moe's.
- Martin once built a device that accurately measured surprise as a school project. People learning what the device did registered "mild surprise". When they found out that Lisa had successfully turned Groundskeeper Willie into a gentleman, it went higher.
A season 2 episode of Laff-a-Lympics employed an applause meter to gauge which of the three teams would win a specific event. Mildew Wolf would hold his microphone to the camera, presumably for the viewers at home to vote by applause. Naturally, the Really Rottens got bupkis.
The PKE-meter (see Film, above) is seen frequently on The Real Ghostbusters.

Real Life

As mentioned in the description, the Clap-O-Meter, which was a feature on many game shows in the 60s and 70s. It was supplanted by more accurate forms of audience voting, like keypads.
- There's also the version without an actual meter - you "vote by your applause" and the judges decide who/what gets the loudest applause. Used often in Bikini contests.
When discussing the development of the Wii, Miyamoto mentioned a theoretical "Wife-o-Meter" he used to measure his wife's increasing interest in video games over the years.
Perhaps the most pervasive example ever would be the speedometer in your car. Sure, it's not pronounced the same, but...
British election coverage always features the Swingometer, a needle that is turned from one major party to the other to indicate how many voters have switched their allegiance. Originally a cardboard prop (which was parodied in the election night sketch on Monty Python's Flying Circus as spinning crazily around), it has more recently taken the form of CGI.