Tuck Topeak's Mini 10 Multi-Tool stealthily into your jersey pocket and be prepared for fix nearly anything out on the road. The tiny tool takes up minimal space, and features a mix of Torx, hex, and screwdriver heads to tend to mechanicals and make quick adjustments when you're far away from your garage.
Familiarity: I've used it once or twice and have initial impressions
Picked this up the other day and hope to never have to use on the trails, but happy to know it is smaller than my thumb and weighs almost nothing! Fits great in my pack or could even go in a pocket. Has everything you could want on the trail.