Rurikids, who founded both the Kievan Empire of Rus and the later Russian Empire.
Piasts, who established the Kingdom of Poland.
Ludolfingers, who formed the Holy Roman Empire we know and despise in the later bookmarks.
Karlings, the garden weed of western Europe and descendants of Charlemagne.
Macedonians, arguably the greatest of the Byzantine dynasties.
Komnenoi, Palaiologoi, Angeloi, and Doukas are all several closely related Byzantine dynasties that would go on to rule the Empire.
Ynglings of Harald Fairhair, who gave birth to the Kingdom of Norway.
Munsö, the descendants of Ragnar Lodbrok who were responsible for the creation of Sweden and Denmark.
Trönde, the Norwegian ancestors of the House de Normandie, the Norman Kings of France.
Plantagenet, the Norman Kings of England following the extinction of William the Conqueror's line, and rulers of the Angevin Empire.
Capets, the greatest dynasty of French Kings, largely responsible for the ascension of France over the Plantagenets.
House of Wessex, the dynasty of Alfred the Great and the first true Kings of England.
Mac Ailpin, the first royal dynasty of Scotland.
Balgarsko, the first Kings of Bulgaria.
Bagrationi, the founders of the Kingdoms of Georgia and Armenia.
Árpád, the founders and first royal dynasty of Hungary.
God there are so many more interesting dynasties in CK2 than EU4, lol.
EDIT: Here's some more.
De Cantabria, founded by Alfonso the Great, the first royal dynasty of Spain.
Jimena, led the first efforts to expel Islam from Iberia.
Von Hohenstaufen, Holy Roman Emperors that would for a time go on to rule all of Germany and Italy.