While a bit too light to provide an incapacitating blow to an assailant, SureFire's G3 LED puts out 80 lumens--more than enough to dampen an attacker's enthusiasm when shined right into his eyes.
Better still, it's available in a holster kit that keeps it at the ready and is perfect for a home-defense throw-on-and-go rig. The light itself is virtually indestructible by virtue of its LED diode; there's no filament to burn out or break. Tactical-level runtime is 5.8 hours; normal runtime is 9.4 hours.
It uses standard 123A lithium batteries, and the holster kit has a magazine that contains three spare batteries. $140.