Black & Decker 40V Max Lithium String Trimmer, LST136W
Power and control, if you want the best of both worlds, choose the Black & Decker LST136W 40V Max Lithium String Trimmer. This trimmer has a five position dial you can turn to get max run time or max power. At the lowest power setting, you'll get about 30 minutes continuous run time and still be able to chop down weeds. The highest power setting gives you about 15 minutes of run time, but you'll be able to cut down weeds that others can't touch.
This trimmer is well balanced and weighs about seven pounds with the battery. The shaft rotates to make this an edger when you need one and it comes with a three year warranty. This isn’t an inexpensive trimmer, but the power dial, decent run time and versatility puts it on the top of this list.