The “only one letter left” sound from Scrabble. Honestly a lotta SFX from that show qualify. The Speedword sound effect comes to mind. Anything that sounds like it came from a synthesizer or Casio keyboard fascinates me…the X/O sound from Davidson’s Hollywood Squares also comes to mind.

The TPiR fail horn is too mainstream to be considered “underrated” IMO. That one is well-known even amongst non-diehards. The abridged Card Sharks (Perry) BUST horns on the other hand is somehow underrated for me. I think a lot of it is because I have to listen hard to realize it’s the same horn minus the first two notes.

I second the Pyramid cuckoo.

The BING when a contestant passed spins on PYL.

The Hot Potato 'pass' sound

Many game- and non-game show fans can identify certain game show sfx and apply them to their daily lives.

The TPIR losing horns is a great example, as is the CLANG for the FF reveals.

One sound effect that I don't think ever got it's full respect is the $xxx,xxx Pyramid clock.  That original cue has been used consistently.for over 50 years in the Pyramid incarnations, or used on other Bob Stewart shows.

That cue was so good, other producers had tried to imitate it in their shows.  The last $OTC end game as well as the Every Second Counts end game countdown clocks are examples of the "oftern imitated, never duplicated" category.  I think the Stewart family owned their countdown clock cue outright and never let anyone else use it.

Hence why I nominate it as the most underrated sound effect in game show history.

For some reason, Bill Rafferty's Every Second Counts came to mind first.

Likely because the main game was all softball and goofy "this or that" questions.  Once you got to the bonus round, it went all serious and was pretty intense.