This CVar turns the circle under a selected person/pet on and off.
This CVar wasn't used until an issue cropped up the day after Patch 2.0.12 released. This CVar fixed a ERROR 132 crash for those with out of date graphics cards in Tempest Keep caused by selecting a person/pet while they're standing on a transparent floor .
Changing this setting
In-game, type the following
/console objectselectioncircle setting
Alternatively, you can exit wow, open the Config.wtf file, and add the following line:
SET objectselectioncircle setting
Patch 2.0.12 (2007-04-03): Added either this patch, or sometime before this