I remember hearing that FIFA had added a rule that only goalkeepers could take goal kicks, but in today’s Tunisia-Japan game (I’m posting during halftime), I’ve seen three Tunisian goal kicks taken by a non-goalkeeper.
Was I mistaken about this rule (it made an impression on me since taking goal kicks was my main function as a defender in youth league soccer)? Has it been changed back? Is Tunisia cheating?
I have never heard of this rule, but my knowledge of the game is by no means complete… despite how much time I waste on it. 
This link provides the rules of the game as set out by FIFA. You just need to select the language and a .pdf file will load.
P.S.
I should probably mention I didn’t search the document for the rule as I’m at work, so if anyone checks, please let us know if it’s true.
From the document helpfully found by Racer1
a goal kick can be taken by any player, as Jabba mentions.
other interesting goal kick rules:
kicking into your own goal directly from a goal kick is not a goal.
no player from the attacking team is allowed to be in the penalty area until the kick is taken.
the ball has to be kicked outside the penalty area for it to be in play. if your kick falls short it is retaken.
As has already been said, any player can take it, but if a defender’s taking it, then he’s a player who can’t do much else until he runs up to where the ball is. If it’s the goalie taking it, then all 10 outfield players are free to try and win the ball / join the attack. I think that’s why you’ll find the vast majority of teams get the goalie to take them.
Well whaddaya know…
I’d heard from a self-proclaimed soccer expert that the FIFA rules on goal kicks had changed. I guess I was a little too trusting.
Thanks for the info, everyone.
The only change in the goal kick rule I’m aware of is that, once upon a time, you had to take the kick from the same side of the goal that the ball went out of play. Now you can take it from anywhere inside the six-yard box. Changed in the '90s if memory serves.
Most of the more peculiar situations covered by various rules (such as the ones xash mentions) wouldn’t normally occur in real life of course, but they were worth knowing during childhood Subbuteo tournaments.