Inbreeding and self-fertilization
The first assumption of Hardy-Weinberg that we will violate is the assumption of random mating. We could spend several weeks exploring all of the different ways this can happen, but we don't have time to do that if we're going to get to the stuff that you're more likely to need in your own research. It is important, however, to spend a little time here, because there are ways of departing from random mating that you probably haven't thought of.