While this may surprise some people, I'm sure others won't be as shocked, but I personally really, really dislike Intelligence stats in games. Now, I can understand why it would be there, how intelligent a fictional character may or may not be can be very important. However, I still disagree with it being there.
Why? Well, the answer is a bit complicated, but it basically goes down to what the game can and can not control. See, in an RPG you are playing a character (I know, I was shocked too) that is not you. They are quite probably more physically capable than you, more skilled, and often lead much more interesting lives where they fight dragons and save princesses and what not. To represent this character, who is oh so much more than ourselves, we have a character sheet and mechanics.
We have a Strength stat, because we need to know how strong the character is, how much they can lift and push, how hard they swing. We have an Agility or Dexterity stat to show how quick of hand the character can be, how precise their control of their body is. A Stamina or Tenacity stat for how much damage they can take, how far they can push themselves. Perception for how well they can see things sneaking up on them.
Do you see the similarity in there? Do you see how this makes Intelligence the odd one out? Every one of those stats has something to do with interaction with the world. The physical stats are easy, since you are not physically playing the character (RP is primarily a mental exercise) you need the mechanics to show what you can do. The same is true for Perception, as the game has control of what you do and do not see, what you can and can not hear or otherwise perceive. There is interaction and control there. Even stats like Charisma have this, because the reactions to the use of Charisma come from outside. If an Anti-Social player wants to play someone with a high charisma they can, and the GM can curtail reactions to the player, slanting them by the stat in charisma that the character has.
Now look at Intelligence, that is how you think. When playing a game, you are essentially putting your brain into the character's head. You are seeing through their eyes, hearing through their ears, moving with their body, but it is still your brain. Now this becomes more complicated when you consider the fact that thinking at a different intelligence is really hard. Most people can't even really conceive of it. Sure you know the effects, but actually thinking at a significantly lower or higher level. Try to think with an IQ of 250+, try to think with one of below 75. It is really hard to do. Your whole life you've been thinking with your intelligence, and turning that off is something that most players just can't do. Now yes, the GM can help with higher intelligence, but how long before that boils down to the GM just giving things away? How do you police it otherwise? Who is to say that a character with a low intelligence wouldn't think of that solution? How much do you keep yourself in check based on the difference in Player and Character intelligence? It is almost impossible to get right, and in the 15+ years I've been gaming I don't think I've seen anyone do what I would consider a 'great' job at it, good jobs maybe, but no one did a great job.
Looking into this further, that means to play a character 'right' most people need to get their intelligence stat to a level close to where they feel they think. Then, and only then, they can feel safe in relaxing and just playing the character. That is points taken away from other areas the character may need it, development to give the character a strength because it is unreasonable to expect the player to not make up for it when they are the ones doing the thinking.
So what do you do? Well, who says the stat needs to be intelligence. Make it something that the game can control. For instance, "Knowledge", this is what most systems are getting at with a High Intelligence anyhow so lets just call it what it is. Even really dumb people can have a lot of knowledge. It is also much clearer on the "what you know" versus "what you do not know". The player still has the moment of insight, but there is a hard mechanic, something to be rolled to clearly show if they have knowledge on it or not. The same is true with something like 'Wits'. You aren't taking away the thought, but you are changing how quickly it processes. A character with a higher wits will think faster than the other character. That doesn't mean their solution will be right necessarily, but if both players have the same idea. The one with the higher wits has it first in game.
Both of these move the stat to what stats really should be about, things the game can control for creating the world. Letting the player think as they do without constant worry of "Would my character be able to even conceive of this notion". Yes they are there, and yes a clever debater could turn my argument into semantics. But if you look, there are some key differences that help to fix the problem.
So, if you are designing a game, maybe you should give some thought to shifting Intelligence into something else.
Caveat: Some systems that do things like Super Hero worlds may still need some semblance of an intelligence stat, if only due to the fact that in those worlds "Super Intelligence" is a real factor. That is, a level of intelligence so high it is not humanly possible. In those situations, the person with it may simply need some permission for limited metagaming on what they would think of. Note though that this doesn't remove the problem, it is closer to someone playing the 'Cheat' card in Munchkin.