Power
Didn't somebody sing something about "Knowledge is Power"? We'd have to agree. What's more powerful than knowing you know more than most other people about a bunch of things? You'll have the ability to help people with extensive and accurate information, which is basically its own superpower.
Because of a librarian's help, a reporter could have the statistics that back up her story on the scourge of beri-beri in Ontario right at her fingertips. Because of an intrepid law librarian, a trial attorney could come up with the one case citation that blows the arguments of the opposing counsel completely out of the water.
The ability to win friends, influence people, and back everything up with great information. Now that's power.