If you are interested in a skill monkey, a Fighter 4/Investigator 5 can be a fun combination. The Fighter part is either ranged or melee; the opposite of the Ranger. This stiffens the Investigator up with more hit points, better armor & weapons, and BAB. (Though it may make him a bit MADD.)
At 5th level, the Investigator picks up the Quick Study to add Studied Combat dice to one attack every round.