Merritt's Trifecta tool is a must if you hate carrying around a bunch of different allen keys and sockets. Mike Brennan explains more... 

"The Trifecta multi-tool is a simple, pocket size, and inexpensive tool that is perfect for the most common fixes. Includes a 17mm socket, 6mm and 8mm allen keys in an assembled packaged, so there are no parts to lose. Includes velcro straps to attach to frame." - Merritt