Carl's dangerous robot companions, one of which is still carrying a nuke he keeps quiet about.
When Samantha announces she stole a nuke from Buster and intends to plant it at the college, Carl tells her flatly that she will not be nuking anyone — while privately noting that he has one of those nukes too, still attached to one of the dogs.
He deliberately does not tell her he has a nuke on one of the dangerous robots, which is as much a comment on the doggies as on Samantha's judgment.
Robotic dogs, considered dangerous enough that Carl does not advertise what they are carrying.
Carl's undisclosed nuclear carriers, kept out of Samantha's reach.