Problem
There is a player in my current group who takes a long time to take their turns. A painfully long time!
Typical exchange
Me: Okay John*, it's now your turn to act. The serpent is coiled around your friend, squeezing life from her, but they're on the other side of the pit. What do you do?
John: Alright (pauses and stares into space for maybe 90 seconds).
Me: You're up, John.
John: Can I use my (power which can do an assortment of minor effects, such as prestidigitation (D&D) or hedge magic (Numenera) ) to levitate over the pit.
Me: Although you can use that to hover a small object, levitate is a more powerful ability so that won't cut it.**
John: (Settles into another long think) I shoot the snake with my bow. (Waits for confirmation before rolling a dice)
Me: Cool, go for it.
Jane(who is trapped by the serpent): Eeep!!
John: (Rolls) I hit!
Me: The arrow finds home and both the serpent and Jane are grievously injured.
John: Oh, I wouldn't have done that if I'd known.
Outcome
This kind of drawn out turn gets old quickly. Other players have mentioned it as a major PITA. I have talked to the player, but nothing ever comes from it (He says 'Sure, I understand', but takes long turns regardless).
Questions
Should I introduce stalling (where after a period of time the player misses his turn as his character panics and freezes)?
And if so, do I need a prop, such as an egg timer, to keep track of how long a player has?
Should all players use the timer so John doesn't feel picked on?
Or is there a better approach to dealing with slow players?
* A generic name, not the actual name of my player. I find it better to use player name instead of character name until players are very familiar with their character name and respond quickly to it.
**I hate being the jerk who says 'No'.