I (Sorc) noticed that I automatically target my own pet if I have an enemy player or mob in target and try to face it.
Only happens with bigger pets and only if pet is close to me. It seems as if the /face command would virtually "click" the target I am facing and then selects the pet automatically if it's "in the way". Doesn't happen if I park the pet on the side.
This bug is REALLY ennoying in PvP obviously.