Tic-Tac-Dough had several "red box" categories which allowed a contestant to gain an overwhelming upper hand almost immediately, if played correctly. The most notable of these were...
"Bonus Category", which immediately allowed the contestant another turn if s/he answered a three-part question correctly. The thing was the category board shuffled, and invariably the "Bonus Category" would appear in an adjacent box or in a space that allowed him/her to set up and/or complete a tic-tac-toe. There were several instances where, when this category appeared, the opponent never got to play the game (although they were always invited back to play the next game). Eventually, in the interest of fair play, the category was retired.
"Double-or-Nothing", a modified "Extra Turn" category which added an element of risk — take the box or select another box and lose them both on an incorrect answer. The category board didn't shuffle with this category, allowing the opposing player a chance to play.
The Joker's Wild: Spinning three Jokers on a single spin automatically won the game for that contestant, provided s/he correctly answered a question. More than once, this happened on the first spin, but only once — the first time it happened, in early 1973 — did it result in the opponent not getting a chance to play; the second and all subsequent times it occurred, the opponent was always given at least one opportunity to "catch up" (by continuing to answer questions until they either caught up, won by surpassing the opponent's score or answering incorrectly).
Additionally, like Tic-Tac-Dough, the 1978-86 syndicated version had a number of special scoring categories which contestants could use to either win immediately, catch up or, in the very least, build a huge advantage and pressure their opponent. Most notable were:
"Fast Forward", where a category was read and the player could answer as many questions as they wanted (for either $50, $100, or $200 depending on what else was spun), with the catch that they could stop at any time and keep the money accumulated or risk it on answering the next question correctly; a wrong answer meant all accumulated cash on that question was lost and the opponent could answer just one question for face value.
The "Bid" category: The player decided in advance how many questions he wanted to answer; if he got all of them right, he won the total amount (e.g., three questions at $100 each earned $300). An incorrect answer gave the opponent a chance to answer just one question to win the money. Played successfully, the "Bid" category put pressure on the opponent, but it could also backfire: late in the run, a contestant on her first spin got a natural triple with the category (also awarding a growing jackpot), bid five questions at $200 each (for $1,000, more than enough to win), got the first question wrong, and the champion immediately cashed in with a single correct answer to win the game. Bill Cullen, the host, basically said afterward the contestant's "quick kill" strategy wasn't a very good one, and unlike other quickly defeated contestants on Barry-Enright shows, she wasn't invited back.
Concentration: Rarely did it happen, but when a contestant was able to solve the puzzle immediately upon making the first match of the game on the game's first turn, never allowing the opponent a chance to play. Classic averted this after it instituted a best-of-three (and later, two-losses-and-done) format, while the 1973-78 syndicated version had both players play two matches...but on the original NBC series (and early in the Classic run), it was *tsk tsk* too bad for the unfortunately blitzed contestant.
Sale Of The Century: Had a form of this with the Money Cards on the Fame Game board. Choosing the $25 card late in the game often put the game away for the leading contestant, even with the introduction of the 60-second Speed Round.
Michael Larson, a contestant on the game show Press Your Luck. He memorized the patterns that the board revolves around ahead of time, and became the biggest winner in the show's history by a huge margin ($110,237 in cash and prizes). Immediately after this, the patterns were changed to prevent another such incident, and CBS refused to allow anyone to air the episodes (yes, his taping actually took so long they had to edit it into a two-parter) on TV for nearly 20 years.
Until 2003, Jeopardy champions could win up to five games before being retired. Starting in the 2003-04 season, the producers instituted a "sky's the limit" rule where champions could go on and on winning until being defeated. Towards the season's end, Ken Jennings came along and went on a 74-game winning streak that lasted into the next season.
The Price Is Right: Many pricing games have unwritten tricks or rules that can be easily broken. Note that several of these games didn't actually have these unstated rules until about the very end of the 1970s or very early 1980s, and are never stated outright, but faithful viewers of the show have picked up on these recurring quirks. Examples:
Clock Game: The game often uses multiples of 100 or figures ending in 99. Many contestants have gone right to an $x99 price and gotten it right on the first guess.
Cliff Hangers: The game can almost always be won with guesses of $20-$30-$40 or $25-$35-$45.
Dice Game: Averted early in the game's history, when – despite the fact that a die has no numbers higher than six on it – there could be numbers in the car's price higher than six. Went away once the game settled into its normal rules.
Golden Road: In the final prize, none of the digits repeat. For instance, the contestant is shown $75,_49, and has 1, 4, 6 and 9 to choose from to fill in the blank; based on the unwritten rule, the contestant has essentially an either-or decision (either the 1 or 6).
Hole in One … or Two: An unintentional dent in the course once caused a contestant to win! See here:
Now....or Then: There are always four products that have correct answers of "now", with the remaining two "then." Also, there used to be a problem with recently-made products which were always "now", until the producers caught on and made it possible for these items to be "then" by assigning a lower price through calculation.
Pay the Rent: The least-expensive item of the six grocery items never goes on the lowest platform (i.e., "in the mailbox").
Rat Race: The third prize almost always has had an actual retail price of between $150 and $300, meaning that given the $100 spread either way, a bid of $200-250 can guarantee a pick of at least one rat.
Safe Crackers: The lock tumblers always include a "0," and that zero is intended as the last number, essentially giving the contestant an either-or pick (e.g., $570 or $750?).
Temptation: The prices in the prizes always have two unique digits (e.g., $828 or $1551), giving the contestant an either-or pick for each spot in the price of the car.
10 Chances: The prices always end in 0, or 5 if there is no 0 pick from.
That's Too Much!: The correct answer is neither the first- nor 10th-given price. note For a short time during the 2008-2009 season, the right answer was almost always the second or ninth price, which skewed a Robert Dobkowitz-era rule that the correct answer almost always fell between slots 3 and 8; the production staff let up when fans complained.
Many categories have obvious letters in them: S is usually a good bet if the category is a plural (e.g. "Things" or "People"); Star & Role always has AS in it; Song/Artist and Title/Author always has BY in it; and Food & Drink tends to follow the formula of "X with Y".
Initially, Same Name always contained the word "AND". After literally every contestant started the round with N-D-A, they changed it so that an ampersand (&) would be in place of the word AND. Oddly, they've mostly reverted to spelling out AND.
What Are You Doing? almost always has an -ING ending somewhere. Unlike with Same Name, it seems that contestants are encouraged to call N-G-I first.
The Final Spin of the Speed-Up round can zig-zag this. Originally, its value was just whatever dollar amount the host landed on, thus leading to many cases where a contestant had enough of a lead that his opponents had no chance of victory. (Can't build much traction at, say, $300 per letter.) This was counterbalanced somewhat by adding $1,000 to the value of the Final Spin, but even before that rule change, the Final Spin could become a game breaker if he hits $5,000 (or $2,000 on daytime). Over the years, many a contestant has managed to pull a come-from-behind victory on a $5,000- or $6,000-per-letter Speed-Up, including many who have actually gone from no money whatsoever to victory thanks entirely to said round.
In a non puzzle-related example, there used to be a Free Spin wedge on the Wheel. Countless contestants ended up banking large numbers of Free Spins due to hitting the wedge repeatedly, thus ensuring greater chances of keeping the Wheel out of their opponents' hands. A Summer 1986 daytime episode had the yellow contestant rack up five Free Spins and use them in Round 2, resulting in Round 3 beginning as a Speed-Up for $2,000/consonant — and the blue player won thanks to a $2,000-per-letter Speed-Up. This was finally circumvented by reducing Free Spin to a single disc placed over a dollar amount. It was later retired for Free Play, a wedge which allows the contestant to make any move without penalty, or the chance at one free vowel.
When the five-and-a-vowel Bonus Round debuted in 1981, contestants gave five consonants and a vowel before getting 15 seconds to solve the puzzle. However, a Follow the Leader trend broke out of RSTLNE because they were so common in the English language, it almost assured success. The producers caught on but let it slide until October 3, 1988, when both versions changed the rules to give RSTLNE automatically (to fill in some blanks of the puzzle) with the contestant giving another three-and-a-vowel (until the addition of the Wild Card let them pick another consonant) with just 10 seconds to figure out the answer.
The Prize Puzzle is often this, as merely solving the puzzle awards a trip of some sort that's usually in the $6,000 range. And on many occasions, the winner of the game has a score that, if one takes away said trip's value, drops down to second or third place; fans tend to criticize this because, as you can probably guess, such winners only did so through a guaranteed prize rather than their own skill — and also because quite a few of these players also stink up the Bonus Round.
The Prize Puzzle has managed to up the ante in Season 31, as the round (Round 3) also has an Express Wedge, on which a contestant can opt to stop spinning and keep picking off consonants for $1,000 a pop until he or she solves or calls a wrong letter (which acts as a Bankrupt in this case). However, they seem to realize the potential of a grossly-overinflated payday, as the Prize Puzzles in Season 31 have been noticeably shorter.
For the final round of Match Game, contestants chose one panelist to work with. Richard Dawson was so good at matching that nearly everyone picked him, so the fed-up producers added the Star Wheel in June 1978.