The Stupid Baseball Device... (Spoilers)
This annoyed me.
The signed baseball kept reappearing in ominous fashion so we all knew that it was going to have some major impact on the story.
However every time it appeared I just kept thinking why doesn't Walt just say - hey, that's our baseball, it was in the car. It's like the writers plain forgot their car was already tied to the crime but with another driver. There was absolutely no reason for Walt not to just explain that and ask for it back.
It just made the stupid coincidence of the kid being able to buy the firearm, having got the money from the baseball sale - given to him indirectly from Walt - and then ironically kill his son seem even more ridiculous and contrived.