Get to those hard-to-reach places.
It's always good to have a few stubby Allen wrenches handy. You won't use them often, but you'll be glad they're there when needed. And the best part is they don't have to cost you a dime. Just grab some worn-out hexes from the bottom of the toolbox or some cheap-o silver ones you got with that Ikea magazine rack, and cut the business-end just long enough to sink into a bolt. Keeping a set of 2.5- through 5-millimeter Allens will certainly prove helpful.