These games annoy me. I don't mean real-time or dexterity games like Space Cadets Dice Duel. In those games, it's just everyone playing simultaneously, which is just the type of game it is. I mean games where it's normally a turn-ordered type thing, but there's no actual rule about when a person can do something out of turn.
A lot of beginners seem to think that Magic: The Gathering works this way. They figure that when you cast a creature, your opponent has a second or two to play a counterspell, or that if you move on to your next action fast enough, your opponent has lost the chance to counter. But when you actually learn the real, full rules, you see that there is never a time when it's not clearly defined which ONE player can act at any given moment (exception: any player may resign the game at any time).
Anyway, I recently played Coup, which is a good game in some ways. But it has this issue... when one player declares that they are playing an action, there's no defined rule about who has the chance to challenge the action. All other players can just speak up at any time, and the player whose turn it is just waits a few seconds to see if anyone will challenge. The problem is, it's always disadvantageous to challenge (compared to a different player challenging instead). So all players sit there waiting and hoping that another player will challenge, without any rule about when you have now waited too long. And then if 2 players do both decide to challenge, it's just whoever speaks up first, which might be practically simultaneously. Same with blocking an action.
If I remember right, Munchkin works this way also. When there's a battle, any player can just go and play a card at any time, no rule about whose turn it is. And again you'd rather your opponent play a card before you do.
Anyway, does this type of mechanic annoy anyone else?
(Note that it's different if a game sometimes is this way in practice, like how in Dominion multiple opponents might reveal a Moat at the same time. Or in MTG how players will assume that there was no counterspell after a couple seconds, without specifically stating that they're now passing priority. Or Macao, when people choose which AC they want at the same time. In all these situations, the rules still define an actual order, even if it almost never matters).
