Of the hand tools that are a necessity for every cyclist, first and most obvious are these. (Many people call them by the brand name, Allen.) Bicycle-specific toolmakers make sets, but quality metric keys from a hardware store work fine. Bondhus ($20) is a popular brand, known for its often-copied ball-shaped tip, which allows you to easily spin bolts from an angle, where access is limited. Get the following sizes: 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 10mm. These will work with tiny setscrews on suspension-fork adjuster knobs, crankarm fixing bolts and everything else.