I recall there being a thaumaturgy ritual that made your movement of the mind so precise that you could cut heads off with it but I can't for the life of me remember where I read it
That would be the level 7 Thaumaturgy ritual Chill of the Windsaber. It's from Players Guide to the Sabbat. I don't know which page since I don't have the book near me.
You basically create a very thin telekinetic sheet which you can direct at someone by merely flicking your finger. You don't necessarily need direct line of sight as long as you know where the target is and are familiar with the surroundings. The roll to activate is Perception + Firearms (difficulty 8). The victim can avoid it with a single success on a Dexterity + Empathy (difficulty 9) roll though. You need to snap a small piece of glass to perform the ritual.
There's no other visual effects aside from the target's head popping clean off his neck.