Now, for disorientation and distraction, there is almost no better tool immediately available for self defense today - when coupled with proper use. Ken Good, who used to be with Surefire and now contracts with them, wrote the book on low light tactics and devised some incredible stuff.
Self defense wise, other than to illuminate the threat, you have other options. Briefly, here are some:
Shine the light in their eyes and move. Always move. This can be very disorienting for an attacker because they tend to move where they last saw you. Outflank them and do what you have to (continue the fight or run).
At very close range flash them in the eyes first then use a self defense technique. Head manipulation/throws are good because they do tend to move their eyes away from the light. You will sometimes get a total surprise reaction (like they are thinking "WTF?") and their eyes shut and you can use this to your advantage.
Hit 'em with the light. Light 'em up/then hit 'em with the light.
Strobing is a very interesting use. In tactical training, I have strobed people in the eyes while engaging in shooting training rounds against them and been told it made people start feeling sick to their stomach. Against a drunk or someone similar, strobing the light in their eyes while getting distance or moving to a flanking position will probably be more effective, so long as they keep trying to look at you.
Ken has designed a new light with a built in auto-strobe feature and other cool stuff that should be in production soon: