I have an imperial guard army which I run with an Grey knight codex style Herecticus inquisitor (not legal I know but the Inquisition is like a spice...makes anything you add it to tastier!)
Anyway I was tinkering with the army and came across a configuration which I tried and completely messed up my opponent (Grey knights).
Take a ordo herecticus inquisitor with the psyocculum upgrade, null rod and maybe a condemnor boltgun, give him say 6 or so rogue psykers whack em in a transport and then basically deliver a 36" BS10 STR8 AP1 large blast. killed a paladin heavy list by screening the squad, though if he added a librarian it could have gone differently. So while not perfect (psychic hoods, runes of warding) it proved to be a nasty psychic anti psyker tactic, I thought.
Any other despicable anti psyker tactic out there? (other than runes of warding)