I was just thinking about Agüero since we saw his card yesterday, and wondering whether he should have 5* weak foot? Just because I can recall him scoring plenty of great left foot finishes - he doesn't seem to be particularly weak on his left, to my mind.
So because my job is dull and my life is empty and devoid of meaning, I did some research. Comparing him to some other players over the last two seasons (league only):
As you can see, while he obviously favours his right, he frequently takes shots on his left, and the percentage chance of them going in is roughly the same. I picked De Bruyne, Neymar and Pedro as three high-profile stars with 5* weak foot by way of comparison. De Bruyne's 13/14 wasn't much to go on, but you can see last season he also had a similar success rate with either foot - so equally deserving of 5* as Agüero perhaps?
Neymar however rarely shoots with his left by comparison, and when he does it has a far lower chance of going in. So where is the logic that Neymar has a better weak foot than Agüero? Obviously we'll see later on if Neymar still has 5* on the new game, but surely he doesn't deserve it? Pedro is well known for being two-footed, but you can see here his success rate last season was much lower on his left - might be an anomaly, I don't know.
Used Messi as a 3* player and Robben as a 2* for comparison's sake. You can see that both of them actually had a much higher success rate with their weak foot - but I'm sure in Robben's case it because he only uses his right for tap-ins I should think. Messi is similar, perhaps only using his right from close in - but for both of them at least you can see that the frequency with which they use their weak foot is a lot lower.
TL;DR version - Agüero's weak foot as at least as good as KDB's and better than Neymar's, so either A) Agüero should be 5* or
KDB should be 4* & Neymar 3*.