Before we got TPK'd, my cleric used two rituals (we were low level schmucks):
Gentle Repose - he worshipped Avandra, so as a traveller, he would buy a big shank of meat and GR it so he could eat well on the road.
Silence about got the half the party killed. He put it up during a furneral ceremony for a fallen friend. The Swordmage heard a noise in the woods and decided to investigate. He left the LOS of the group and was ambused by orcs. We, of course, could not hear his screams. The fighter then wanders off to see what happened and was attacked as well (she at least stayed in sight so the rest of us could respond).
Quite frankly, the group deserved its eventual TPK (well, my cleric left them to their deserved fate). But that is another story.