If you could attend any show, past or present...

[TimK2003]

For a specific episode, I would've liked to be in the audience for the final episode of Rhyme & Reason. 

With Pat Harrington & Charlie Brill allegedly heading up the set "break-down" committee, it sounded like much of the audience could have taken home a piece of the set!

[BillCullen1]

I've been fortunate to see about two dozen shows in person between living in NYC and going to L.A. in CA. So I'll pick shows I never saw in person. Dawson Feud, Ludden PP, Kennedy NTT. Back to before I was on Earth, I'll pick the classic G-T shows WML, IGAS and BTC. A present day show I would go to see is PYL with E. Banks. I've seen Strahan Pyramid and Baldwin MG since they tape in NYC.

[Clay Zambo]

Oh, so many. But maybe the first taping of ABC Password?

[Unrealtor]

They taped 5 more shows the following day (as normal), THEN they went and tweaked the board with 5 different patterns and a slightly slower speed. CBS/Carruthers actually didn't overhaul the programming until 13 more weeks had passed, presumably to see if the ratings would hold up before spending the money to completely reconfigure the board.

I wonder whether the time required to design and make the changes to the electronics might have been a factor as well, so they waited for a time when there would be a longer than normal break at the end of the "season." I'm assuming from the presence of fixed patterns that everything was hard-wired rather than being driven by any kind of integrated circuit, so sextupling the number of patterns would have required replacing that entire part of the circuitry.

(Now this topic has me wondering about the internals of how the software that drives the 2019-present board determines what order to bounce around the board, and what level of complexity the system that drove the score displays had. Younger me, watching a few years later, assumed that it was doing the addition for them because it was too fast to be someone entering the result after calculating it, but older me thinks that's a big ask for a one-off custom electronics job.)

[geno57]

1) The Downs / Clayton Concentration.

2) The original (NBC) Match Game.

3) The Cullen Price Is Right.

I would’ve had a field day at 30 Rock when I was a kid!

[Mike Tennant]

As a Barkerphile, I'd settle for either Truth or Consequences or The Price Is Right during his tenure, though for Price I'd prefer the first decade or so of hour shows.

[jcs290]

My 8 year-old self would say Nick Arcade since the only time I was able to visit Nickelodeon Studios was just after their 1st season wrapped (the only set piece visible on the tour was the yellow and orange lightning floor graphics).

[danderson]

The Downs / Clayton Concentration or Perry SOTC.

TJW(either Barry or Finn).

[tomobrien]

The aforementioned Dotto episode.  Would also be curious to be in the audience for The $64,000 Question to see how the audience excitement level compares with that of WWTBAM.

And two vaguely remembered shows from my childhood:
Make a Face (Bob Clayton's first hosting job)
Alumni Fun

[rebelwrest]

I would like attend the daytime $ale of the Century during the shopping endgame.  I wanted to experience the atmosphere of seeing someone staying for more than five days, going for a six digit payoff, and taking HUGE risks to go for the payoff. I think what made $ale of the Century so different is that it was the first game show in daytime to have a episodes long story arc.  There was long championship reigns for contestants in the past but there was never the added danger of losing it all (except for the original $ale of the Century but it wasn't as life changing as the 80s version was).  In terms of producing compelling story arcs, NBC was the network for them in prime time and daytime game shows.

[TimK2003]

A show I would have liked to see was either version of (The New) Treasure Hunt.  Perhaps one episode in the audience and one episode behind the scenes.

Would have been fun to see how they scurried to set up the correct props and prizes/klunks once the contestant chose box number.

[alfonzos]

I can attend a taping of the original series of "Concentration"? Okay, Devil here's my soul!