Gameplay that revolves around unlockables. Examples include Race the Sun, LĂĽftrausers, FTL and Tower of Guns. You know, where you start with jackshit equipment and have to beat in-game "achievements" to unlock upgrades and game modes. It's the biggest case of "artificial restraint" that I've ever seen. It's only there to pad gameplay, and it's one of the suckiest ways to do so.
On a related note, not having all content available in a single playthrough. If I have to play New Game+ just to get to play the last chapter or get the true ending, that game has lost me. Especially considering that many games aren't worth more than a single playthrough, padding the game with crap like this ain't gonna work. I'm not talking about "choice and consequence"-based content, where the content is available but you have to choose which part of it you want. That's a more organic approach to encourage game replay.
Damned Registrations mentioned "developers trying to prevent gamers gaming their games". This is a great point because once a developer releases a game it is out of his hands HOW others play the game. Imposing artificial restraints to try to herd gamers through the game is not just lazy, it's rude. A good example from Alien: Isolation is to FORCE the player to "see" a passcode at its source before it can be used...even though the passcode is ALWAYS the same, the source is ALWAYS a computer and ALL COMPUTER LOGS are saved automatically for all time once they've been discovered. It's a reaction to "the code is always the same, but we want players to go through the motions of finding the code" that DOESN'T involve the obvious solution: Random codes. UUW2 (1993) had several passwords that were randomized for each playthrough, clearly the coding marvels of 20+ years ago have been lost to the mists of time or somesuch. Or maybe CA (just to name an example) just fucking suck at their jobs.
Along these lines, invisible walls. "Oh look, I can shapeshift into a parrot and fly across the gap to *thud* "Nope. You're not supposed to go there yet, so you don't get to go there." says the developer, because Reasons. Richard Garriott knew how much this sucked, which is why several Ultima games can not only be broken, but broken in hilarious ways (See: Doug the Eagle's website, especially "
Ocean Travel Without A Boat")
QTEs have been mentioned. Just...stahp.
I don't mind (lock-picking) minigames as long as they're worth a damn, which is not always the case. I get the feeling that the best-case scenario would be to have the mini-game start easy at first then get a little harder, then get easier towards the endgame because by the time you're going through the final act of the game you don't really want to waste a minute on a stupid mini-game to get past an insignificant obstacle. It could be written off as "the player gains an automated lockpicker that does the job for him in 10% of the time". Or maybe the game protagonist gets really good at kicking down doors.
There are other "de facto" standards of modern game design that bother me, but I can't think of them right now.