The Tradesman Multi Tool from Blackburn is a well thought out bit of kit. This will pretty much sort most bikes out on the trails with a wide range of tools to suit most parts, including a disc brake spreader and a quick link chain tool to fix up that broken chain. It even cleverly stows a replacement link within the tool. With its L shaped tools you get more leverage to undo some of the most stubborn bolts, whilst still being compact and lightweight.
Blackburn has really thought out the spec of this tool to make it suit Moutain Bikers needs.
* 18 functions * Quick link storage * Tools include: T25, T30, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 8mm allens, disc brake pad spreader, flathead screwdriver and quick link chain tool compatible with 12 speed and fewer gears * Weight: 135 grams