They're some of the cutest, best-coiffed, and most camera-aware men on earth. But take a look a close look at Hugh Grant, Tom Cruise, Chris O'Donnell, and Christian Slater. They're unibrowers. Right between their sparkling and emotive eyes grow straggling, tufted, unbroken hedgerows. They could try fertilizer and go for the Bert effect that Sesame Street prizes so much. But Kevyn Aucoin, author of The Art of Makeup, recommends a more moderate path. ''A really manicured eyebrow on a man can be really scary,'' says Aucoin. ''Then again, you don't want a small flock of birds to come nest.'' Our celebrity unibrowers can rest easy, though, since the rest of their mugs get high marks. ''Hugh and Tom have such beautiful, perfect faces,'' says Aucoin, ''the little bit of hair makes them attractive in a Cro-Magnon sort of way.''