They're the strongest anchor out there and can safely hold 40-lb. They're standard issue in microwave-installation kits, for instance.
Toggles are also a royal pain to install.
A traditional toggle consists of a single long machine screw that's threaded into a folding spring-loaded wing assembly that expands once it's behind the wall. Because the large pilot hole needed for the wings will swallow the machine-screw head, you have to use whatever fixture you're installing as a washer. After unthreading the wings from the screw, you insert the screw through the fixture and rethread the wings. Then, holding the fixture steady with one hand, insert the folded wings into the hole. Once the wings have expanded behind the wall, you pull back on the screw with your second hand to keep tension on the wings while tightening the screw with your third hand.