Holdover tent-poles Teenage Mutant Ninja Turtles and Guardians of the Galaxy maintained the top spots at the weekend box office, while the new openers trailed behind. But, while it was expected that Let's Be Cops and The Giver would open in the teens, the biggest surprise of the weekend was The Expendables 3, a franchise pic which should have easily opened in the $20 to $25 million range, but instead floundered with an estimated $16.2 million.