Monster Manual II, pg. 146 - 147 has an ugly little critter called the Meenlock. It comes with two (Su) abilities, at will, that are fear effects that either render their foe catatonic (i.e. helpless) or deal 1d4 WIS damage. Normally ECL 8 (4 Aberration HD, +4 LA), would not be worth it. But for a gestalt game (specifically an arena), what can we stack on top of these guys to tweak out the fear factor? Both of the abilities are CHA based, so something with Binder or Hexblade (Dark Companion) to help lower saves might be interesting. I've read the fear handbooks and gotten a few decent ideas so far, but I'm sure there is plenty I'm missing.
The fact they get Dimension Door as (Su) every 2 rounds, and 300' telepathy just helps make these guys that much more interesting.
So would they be worth the optimization effort? Or am I just too easily impressed by the value of these tiny buggers?