Pedro's Y Wrench
If you've never seen the Pedro's Y Wrench (or one exactly like it), may we suggest going into any local bike shop and asking to borrow an Allen key? Wrenches like the Y Wrench are ubiquitous to every bike tech's bench and serious pedal-head's garage for one main reason: leverage. The Y shape provides great grip and twist-ability, plus it's bigger than your buddy's back jersey pocket, and bright "Pedro's yellow", so you'll see it if it's sneaking away from your toolbox.