Also known as Allen wrenches, these are a must-have for any avid cyclist.
Bicycle-specific toolmakers make sets, but good-quality metric keys from a hardware store work fine. Bondhus is a popular brand, known for its often-copied ball-shaped tip, which allows you to easily spin bolts from an angle when access is limited. Get the following wrench sizes: 1.5, 2, 2.5, 3, 4, 5, 6, 8, and 10 millimeters. These will work with tiny setscrews on suspension-fork adjuster knobs, crankarm fixing bolts, and everything else.