Oh goddess of Squashed Animals, which nowadays mainly consists of animals that have been run over by carts. Recently Aniger has been growing a bit more powerful among the gods of the Disc, because better roads and faster carts mean more drivers thinking: "Oh god, what was that I hit?" (see The Last Hero). Aniger has not yet featured in a Discworld novel, or even a painting, but has been mentioned a few times.
Mrs Georgina Bradshaw, in her handbook Mrs Bradshaw's Handbook, mentions that in the town of Little Swelling there is a popular shrine to Aniger that attracts her believers. It is set in the cobbles in the middle of a bridge. Once a year it is scrubbed clean of the remains of small dead animals and a wreath is laid, amidst much ceremony. The local general stores sells iconographic postcards of the shrine and helpful books on how to recognise track-kill and all the things you can cook it into.
Technically, Aniger may rate as Discworld's second known oh god (after Bilious).