Park's MT-1 "dogbone" multi-tool. As a take-along tool it's much lighter and smaller (and cheaper) than any of the Swiss Army Knife type multi-tools and does nearly everything I need. It has 3,4,5,6 and 8 mm hexes, 8,9 and 10 mm boxes and a small flat blade screwdriver. The larger hexes are positioned to have good leverage so the thing is really useful. Combined with a small chain tool it's a pretty complete on-the road repair kit.