The unknown Wraith beam has been seen in use once. Major John Sheppard observed it when the Wraith were culling Orin's planet. After a dart was seen using its culling beam, it flew over an area where a beam formed and went into the sky. The purpose of this beam is unknown, but it's presumed the beam is meant to tag the planet as having been culled as a means of signaling any other hive ships and cruisers that they can't cull the inhabitants until they recover. Considering it was active during the rest of the culling and caused no apparent damage, the beam is most likely not a weapon. (SGA: "Letters from Pegasus")
beam fully formed