I might not be able to come up with five guys for this, but this role is decisive and often over-looked. Like the picadors in the bull-ring, whose job is to wear, vex, annoy, and tire the bull out for the matador to finish him off, the picador's job is to inflict pain, suffering, and vexation and begin to create the conditions to make a selection. There's the cliche about "the riders make the race." Well, it's these guys who do that on the climbs.
For teams with multiple possible leaders, like say Rabobank or Liquigas, it becomes difficult to figure out--and maybe won't be figured out until they're on the road, who gets the short straw.
In the US Postal/Discovery days, guys like Heras, Rubiera, Azevedo, and Beltran did the deed. (In fact, one of my favorite moments in a Grand Tour occurred on the first ramps of l'Alpe D'Huez the year Beltran drilled it so hard that he dropped Armstrong momentarily).
So, there's an art to putting in a couple of kilometers at a pace that torments everyone without causing an obvious gap. There's also a managerial skill in convincing guys--many of whom, almost by definition, could think of themselves as g.c. riders, to blow themselves up for someone else. Riis's leadership in the 08 Tour worked well in getting the Schleck's to set up Sastre.
Personally, my favorite set-up guys are Jens! Voigt and Fabian Cancellara--sure they're not mountain goats, and that's what makes it so fun to watch when one of them has gone in an early break, then sits up and gives another k or 5.
But who's best at this role (and who winds up drawing the short straw on Radio Shack?)