Brennos

Brennos, chieftain of the Senones, led an army of Cisalpine Gauls in their attack on Rome in the Battle of the Allia, in 387 BC. Another Brennos was one of the leaders of the army of Gauls who attempted to invade and settle in the Greek mainland in 278 BC. After a looting spree and after managing to pass Thermopylae by encircling the Greek army and forcing it to retreat he made his way to the rich treasury at Delphi but he was defeated by the re-assembled Greek army.
It has been debated whether Brenno was an actual given name or rather a title.