Hollow Man proved anything but invisible at the box office over the weekend, debuting at No. 1 with an estimated gross of $26.8 million. If final numbers hold up, the Kevin Bacon thriller would go down as the biggest August opening to date (beating The Sixth Sense, which last summer earned $26.7 million in its first weekend). Last week's top film, Nutty Professor II: The Klumps, slipped a grotesque 58 percent, taking in $18 million for second place. Newcomers Space Cowboys and Coyote Ugly were close behind in third and fourth place, grossing $17.6 million and $17 million, respectively. What Lies Beneath held steady in fifth with $13.9 million.