There's a bit of an issue with your question. A pretender, by definition, has a claim to the throne while someone taking a throne with no traceable claim would simply be an invader, a revolutionary ect.

There are plenty of cases of pretenders taking crowns from the rightful owner to secure their junior claim. The one that comes to mind most readily is the English Civil War and the installment of William of Orange.

Were you looking for complete removal of dynasties by people that had no claim at all? Like the Norman invasion of England. Its hard to settle in on what you want to know hehe.