Well, looking at the skill list for a second:
Acrobatics: Combat, and Physical SCs
Arcana: Monster Knowledge, Ritual SCs including often in combat SCs
Athletics: Combat, and Physical SCs
Bluff: Social SCs, sometimes useful for bypassing encounters entirely or achieving surprise
Diplomacy: Social SCs, sometimes useful for bypassing or ending encounters early or getting better options
Dungeoneering: Monster Knowledge, Survival SCs
Endurance: Disease, Survival SCs
Heal: Combat (mostly for giving saves, so less useful investment past Heroic), lesser role in investigative or Survival SCs
History: lesser role in Investigative, Ritual, or Social SCs
Insight: Social SCs, sometimes useful for avoiding surprise
Intimidate: Social SCs, sometimes useful for avoiding combat or ending it early
Nature: Monster Knowledge, Survival SCs, some Ritual SCs
Perception: Combat, generic Exploration as well as Investigative and Survival SCs, lesser role Social and Physical SCs
Religion: Monster Knowledge, Ritual SCs, including often in combat SCs
Stealth: Niche used for scouting and rogues in combat, Survival SCs
Streetwise: Social SCs
Thievery: Delaying Traps, lesser role in only a few SCs
So, looking over that, Streetwise, Thievery, Stealth, History.