Probably Gonzales, Laver, Sedgman, Budge, and Vines. They could all get hot, and had the physical ability to raise their games an extra gear. Not someone like Kramer, who was incredibly consistent every day, but didn't have the "hot" end, and was, in Gonzales' words, "not a natural athlete, and not too fast or quick." Others, like Perry, Newcombe, Smith, among others, simply didn't have the range of great shots to lift their games above the normal. Some lacked great footspeed, like Trabert, Sampras (who didn't usually need it, except on clay), Becker (slower than Sampras).