Any D&D 4th Ed. player knows that a well-rounded party needs a controller, a striker, a defender, and a leader.
Most often, I think a character's function and contribution to the party is entirely measured in terms of what role(s) they fill. But there's more to be considered than that - especially in non-combat encounters. Every class has specialized or "Recommended" skills associated with it, as well as other elements.
I'm primarily focusing on skills with this query. What are good configurations for a four-character party that not only fill each necessary role but also have each skill well-trained by at least one character? (I say "most skills" because there are 17 skills and most characters are only trained in 4. This would leave one skill unaccounted for in a party of 4 PCs.)