I was browsing through this guy's science blog and came across this article - it covered a few different instances of strange whale jaws, most of which were normal formations, but I found the deformity referenced the most fascinating.
"If you've ever read anything about sperm whales Physeter macrocephalus you'll have read the assertion that broken and deformed lower jaws have often been reported in members of this species. It's nice to know this, but why are these broken and deformed lower jaws never figured? Here is perhaps the ultimate example: this is the lower jaw of a mature male, about 12 m long, harpooned in Antarctic waters in January 1959. The dentaries curve to the right, then form a spiral, and note that the teeth on the outside of the spiral have been worn down to stumps, or lost (Spaul 1964). This is not the only sperm whale individual in which a coiled lower jaw was reported, and there are also quite a few additional records of sperm whales with strongly bent, hooked or crooked lower jaws. These deformities have been hypothesised to have arisen in diverse ways: as heritable malformations, as the consequences of disease or malnutrition, or as pathologies that resulted from combat. The important thing is that the individuals that possessed these jaws were generally described as healthy and otherwise normal (such was the case for the individual shown here). This strongly indicates that, however sperm whales obtain food, they don't need nice neat 'normal' lower jaws to do it. Exactly how sperm whales do obtain their food has been the topic of great debate, and it's such an interesting area that I'm not about to begin to cover it now (sorry, I would if I had the time)."