Area: A rippling wave of wind (or whatever medium you happen to be casting in) rushes away from you. The wave only has one effect: all non-magical sources of light (and darkness, if any exist on your world) it touches are instantly doused. Large sources (like bonfires) are doused only if they're entirely in the area of effect. A source that is only partially in the spread flickers with the wave, but does not go out. You also treat this as an 'area' casting of Dispel Magic that affects only light- or darkness-producing spells.
Target: A burst of air (or whatever medium you happen to be casting in) rushes from you to the target. Any non-magical sources of light or darkness in the possession of the creature (or on the object) are instantly doused. You also treat this as a 'targeted' casting of Dispel Magic that affects only light- or darkness-producing spells and magic items.
In either case above, if a spell or magical item becomes affected, any light- or darkness-producing effects are supressed for 1d3 rounds. Spells stored in wands are unaffected, even if they produce light or darkness.
Fires and such that are doused by this spell can be relit normally. This spell can not be used to counterspell a light- or darkness-producing spell.
This spell was inspired by Shawn Girard's "Dispel Light", as posted to rec.games.frp.dnd.