When you’re running* a game, avoid making a player lose a turn. Game design doesn’t have many universal truisms, but this is one.

Players play games to fulfill needs. And when you prevent a player from taking an action, you’re literally preventing that player from having any ability to satisfy those needs. Paralysis, fear effects, stunning, etc. are all conditions that sound cool or thematic, but actually undermine the reason people play games to begin with: to see the outcomes of their actions, to improve at the actions in play, to relate to one another, and to exercise choice.

Lio by Mark Tatulli

Instead, consider the following when you intend to create tension or anxiety by restricting a player’s ability to act:

• Consume a resource to perform an action (which at least allows the player to decide whether acting is worth spending that resource)
• Take actions at increased resource costs
• Act at reduced efficiency or effectiveness (e.g. move or attack but not both, attack at a damage penalty, heal using a die one step down from the standard die, draw one fewer action card, etc.)
• Act as normal with the input of another player (e.g. The cleric demands the player “Snap out of it!” which allows players to decide upon their own criteria for allowing each other to exchange a less effective action for a greater one)

If you’re not letting a player play, why are they at the table?

Note that, in most cases, it’s perfectly acceptable for a player to deprive a GM character of an action. The GM is often in the position of taking actions for multiple entities, and the nature of the GM’s participation is different from the way the player interacts with the game. Indeed, games that rely on creating strong tactical advantage (D&D 4e, Pathfinder, etc.) can actually benefit from depriving GM entities of their actions, as it streamlines play and hastens decision-making back into the players’ hands.

* or designing!