Maybe it isn't my place to tell a player how to build their character, but...
The social adept with Magic 5 and negligible combat skills who wasted most of that Magic to get Improved Reflexes II instead of focusing on, well, social stuff.
The Manipulation/Illusion Mage with no other combat abilities to speak of (including spells) who wastes a spell slot at chargen on Improved Reflexes II AND buys a sustaining focus to go with it.
I've tried to point these things out politely in the form of suggestions, and in response I'm pretty much getting shrugs. I'm trying not to become too annoyed with that.
But the whole gaming the system to get abilities that really wouldn't be consistent with the character concept as presented in conjunction with the rest of the characters' build kinda is annoying.
So I decided to just say no, and told them to spend the points elsewhere instead of the Increased Reflexes.
And then, of course, there is the rigger who thinks that Demolitions skill is more important than something like, say, Electronic Warfare. Pointing out that his boat he's so proud of building WILL, in all probability, get hacked if this remains the case doesn't even make a dent...
Gotta love your players.