Bicycles have a wide variety of complex components that need tweaking from time to time. Since it is inadvisable to carry an entire toolbox with you, and Bicycle Repair Man has a limited range, it’s best to carry a compact tool.
For a basic multi-tool, go with the Park Tool I-Beam Mini, which covers the basics and slips easily into a jersey pocket. If you’d like to go full on Macgyver, we highly recommend the Blackburn Tradesman, which includes every tool needed for your cycling survival.