No one tool gets more use on our bikes than the humble Allen wrench. Use one enough, and you'll wear it out. If you've used your favorite multi-tool or three-way enough to have rounded off its six sharp edges, it's time to literally cut your losses. If you snip off the worn-out end, you've got a fresh wrench underneath. It may take some effort because high-end multi-tools are often too strong for a hacksaw, so you'll need a Dremel tool. Clamp it in a vice, slice it flat, and gently file the end.
On the other hand, if you've used a classic L-shaped allen wrench enough, you might learn a few tricks to speed up your workflow. When you're spinning in a loose bolt, you need high a RPM but low torque. You can twirl the wrench between your thumb and forefinger, but you can't do that continually without resetting your grasp. And if there's any friction at all on the bolt, you won't be able to apply enough torque to gain any speed. Instead, there's a method you'll catch professional mechanics using. Hold the long end of the wrench between your index and middle finger, with the bent end facing your palm. You can twiddle your thumb around the tip and you get an instant low-power power drill. Even if the bolt is binding slightly, you can still push through it. Just think of what you can do with all the time you'll save? You could learn to juggle!