* GameBreaker: As a guideline, any rule favoring a specific player is against the spirit of the game. It is, however, quite possible with a bit of ingenuity to rig the game with a well chosen and timed sequence of new rules that do not favor any one player. Introduce "players may play any number of cards, with the top card counting as the played card", but do not reveal it yet. Next time you win, introduce "players may play any card on any other card", and use both rules to win on your next turn, silencing all complaints with "New rule, and previously introduced new rule" (and watch the other players go "wtf?"), then introduce "dealer plays first" when you win that game, causing you to win all other rounds with ease. Don't expect anyone ever to play with you again, however.
** GameBreakingBug: It's quite easy to make a rule which can break the game and prevent anyone from playing anything at all. When this happens, the players generally take a vote on whether to keep the rule or not.
*** And that's not even getting into players from different groups each playing with incompatible rules. More the once the game has come to blows...
** Some players have tremendous difficulty with the '[[spoiler:the joker is the 9 of diamonds]]' rule, which is one of the basic rules in many variants. It is exactly what it says: [[spoiler:any joker is considered equivalent to the 9 of diamonds when played]]. That rule is simple when compared to some others. Here are some fun ones to add, among other possible rules:
*** All clubs are called spades.
*** All Diamonds are clubs.
*** Can a Diamond be played on a spade?
*** Can a diamond be played on a club?
*** What must be spoken, if the played card is the 7 of Diamonds?
*** What is the proper penalty to call for failing to speak what is required?
*** The respective answers are [[spoiler:no, yes, "Seven of spades, have a nice day" and "Failure to call a club a spade, failure to say "have a nice day".]]
** This trope also occurs when there's a rule that's been introduced that a player just can't figure out, and they always end up getting penalised for breaking it without knowing why. One example is "Failure to be a Thwiggle-Thwoggle", which is [[spoiler: not hooking your thumbs after playing your card.]]