If you tend to leave your tools when you need it most, consider the all in multitool for your bike. It stays on your bike, nestled into the crank hollow and secured by a powerful magnet, so you never forget to take it with you.
The steel-bodied multitool comes with 6 interchangeable bits, which magnetically attaches to a socket that can turn 90 degrees for convenience.
The bits include four Allen keys from size 3 to 6mm, a T25 Torx and a #1 Phillips screw bit, but you can replace them with other bits to suit your needs.
They say 99% of your repairs can be handled with just this one tool.